These are the points Margaret Killjoy makes in setting Post-Civ apart from anarcho-primitivism. Let's go through them one by one and I'll demonstrate how they're little more than strawmen, and show that Post-Civ is really no different than anarcho-primitivism in substance or practice.

We’re Not Primitivists. It is neither possible, nor desirable, to return to a pre-civilized state of being. Most of the groundwork of anti-civilization thought — important work, mind you — has been laid down by primitivists. Primitivists believe, by and large, that humanity would be better served by returning to a pre-civilized way of life. This is not a view that we share.

Anprims don't actually believe it's possible or desirable to 'return to a pre-civilized state of being'.

From A Primitivist Primer:

The fact is that anarcho-primitivism is not a power-seeking ideology. It doesn’t seek to capture the State, take over factories, win converts, create political organizations, or order people about. Instead, it wants people to become free individuals living in free communities which are interdependent with one another and with the biosphere they inhabit. It wants, then, a total transformation, a transformation of identity, ways of life, ways of being, and ways of communicating. This means that the tried and tested means of power-seeking ideologies just aren’t relevant to the anarcho-primitivist project, which seeks to abolish all forms of power. So new forms of action and being, forms appropriate to and commensurate with the anarcho-primitivist project, need to be developed. This is an ongoing process and so there’s no easy answer to the question: What is to be done? At present, many agree that communities of resistance are an important element in the anarcho-primitivist project. The word ‘community’ is bandied about these days in all kinds of absurd ways (e.g., the business community), precisely because most genuine communities have been destroyed by Capital and the State. Some think that if traditional communities, frequently sources of resistance to power, have been destroyed, then the creation of communities of resistance — communities formed by individuals with resistance as their common focus — are a way to recreate bases for action. An old anarchist idea is that the new world must be created within the shell of the old. This means that when civilization collapses — through its own volition, through our efforts, or a combination of the two — there will be an alternative waiting to take its place. This is really necessary as, in the absence of positive alternatives, the social disruption caused by collapse could easily create the psychological insecurity and social vacuum in which fascism and other totalitarian dictatorships could flourish. For the present writer, this means that anarcho-primitivists need to develop communities of resistance — microcosms (as much as they can be) of the future to come — both in cities and outside. These need to act as bases for action (particularly direct action), but also as sites for the creation of new ways of thinking, behaving, communicating, being, and so on, as well as new sets of ethics — in short, a whole new liberatory culture. They need to become places where people can discover their true desires and pleasures, and through the good old anarchist idea of the exemplary deed, show others by example that alternative ways of life are possible. However, there are many other possibilities that need exploring. The kind of world envisaged by anarcho-primitivism is one unprecedented in human experience in terms of the degree and types of freedom anticipated ... so there can’t be any limits on the forms of resistance and insurgency that might develop. The kind of vast transformations envisaged will need all kinds of innovative thought and activity.

So, primitivism is not an attempt to turn back the clock to the stone age as Killjoy asserts, it's rather taking action to set up alternate, sustainable and thriving ways of life for the purposes of prefiguration. It's looking forward to create forms of resistance, setting up living refuges parallel to industrial society to house free people, and putting together the infrastructure anarchists need to thrive within the shell of a rapidly collapsing civilization. To prepare ourselves for the coming torrent of disasters that this dying civilization will bring and help each other not only survive these disasters, but prosper in the ruins of the old world.

It isn't an attempt to return to the past, it's a concerted effort to look to the future and create sobering, but necessary mechanisms to cope with the continuing decay of civilization.

Primitivists reject technology. We just reject the inappropriate use of technology. Now, to be fair, that’s almost all of the uses of technology we see in the civilized world. But our issue with most primitivist theory is one of babies and bathwater. Sure, most technologies are being put to rather evil uses — whether warfare or simple ecocide — but that doesn’t make technology (“The application of scientific knowledge for practical purposes.”) inherently evil. It just means that we need to completely re-imagine how we interact with machines, with tools, even with science. We need to determine whether something is useful and sustainable, rather than judging things purely on their economic or military value.

This point is the most obtuse of all because it completely misunderstands the anprim definition of technology.

From A Primitivist Primer again:

John Zerzan defines technology as ‘the ensemble of division of labor/ production/ industrialism and its impact on us and on nature. Technology is the sum of mediations between us and the natural world and the sum of those separations mediating us from each other. It is all the drudgery and toxicity required to produce and reproduce the stage of hyper-alienation we languish in. It is the texture and the form of domination at any given stage of hierarchy and domination.’ Opposition to technology thus plays an important role in anarcho-primitivist practice. However, Fredy Perlman says that ‘technology is nothing but the Leviathan’s armory,’ its ‘claws and fangs.’ Anarcho-primitivists are thus opposed to technology, but there is some debate over how central technology is to domination in civilization. A distinction should be drawn between tools (or implements) and technology. Perlman shows that primitive peoples develop all kinds of tools and implements, but not technologies: ‘The material objects, the canes and canoes, the digging sticks and walls, were things a single individual could make, or they were things, like a wall, that required the cooperation of many on a single occasion .... Most of the implements are ancient, and the [material] surpluses [these implements supposedly made possible] have been ripe since the first dawn, but they did not give rise to impersonal institutions. People, living beings, give rise to both.’ Tools are creations on a localised, small-scale, the products of either individuals or small groups on specific occasions. As such, they do not give rise to systems of control and coercion. Technology, on the other hand, is the product of large-scale interlocking systems of extraction, production, distribution and consumption, and such systems gain their own momentum and dynamic. As such, they demand structures of control and obedience on a mass scale — what Perlman calls impersonal institutions.

As you can see, anprims have no qualms with what Killjoy would call 'useful and sustainable' i.e. items that don't require "large-scale interlocking systems of extraction, production, distribution and consumption". Killjoy even admits to rejecting "almost all of the uses of technology we see in the civilized world", so what Post-Civs propose is really exactly the same as what anprims propose... Tools that can be produced locally, without hierarchy/control/coercion/obedience and without centralized extractive industrial society. This is not defined as technology by anprims. Sustainable tools that improve our lives without destroying our ecosystems are fully embraced by anarcho-primitivism, just as they are by Post-Civ.

Killjoy continues:

Primitivists reject agriculture. We simply reject monoculture, which is abhorrent and centralizing, destroys regional autonomy, forces globalization on the world, and leads to horrific practices like slash-and-burn farming. We also reject other stupid ideas of how to feed humanity, like setting 6 billion people loose in the woods to hunt and gather. By and large, post-civ folks embrace permaculture: agricultural systems designed from the outset to be sustainable in whatever given area they are developed.

Again, they're strawmanning anprim philosophy by claiming anprims want to force 6 billion people to be hunter gatherers. Anprims are not trying to enforce a program on anyone, let alone the entire planet. Anprims are simply exploring possible alternatives to industrial civilization. These alternatives being discussed almost always include producing food in some manner due to the simple reality that there's very little wilderness left in the world to forage from.

Anprims talk very favorably about the long history of indigenous peoples deliberately attending rainforests to encourage the proliferation of useful and nourishing plants, which is an example of horticulture that isn't destructive. Anprims fully embrace the re-establishment of Earth's food forests, which will require a concerted human effort to replant and cultivate.

This is how Zerzan describes agriculture:

1. agriculture is the will to power over nature, the materialization of alienated humanity’s desire to subdue and control the natural world; 2) agriculture inevitably destroys the balance of nature, leaving biological degradation and ecological ruin in its wake; 3) agriculture is “the beginning of work and production,” generating an increasingly standardized, confined and repressive culture; and 4) agriculture leads inevitably to the rise of civilization.

What's being described here is precisely what Killjoy calls 'monoculture'. Killjoy then borrows a non-anarchist phrase (permaculture), without defining it, but permaculture and food forests are incredibly similar concepts.

Permaculture:

Permaculture is an approach to land management and settlement design that adopts arrangements observed in flourishing natural ecosystems. It includes a set of design principles derived using whole-systems thinking. It applies these principles in fields such as regenerative agriculture, town planning, rewilding, and community resilience.

Food forests:

A food forest (or forest garden) is a garden that mimics the structures of a natural forest, with multiple layers of plants stacked vertically to increase overall production.

As you can see, food forests and permaculture are closely related concepts with the only real difference being that permaculture is a copyrighted brand used to generate profit by a handful of Western white men who write guides, teach courses and sell 'permaculture certificates' to the public while also fully embodying white male 'guru culture'.

Food forests, for all intents and purposes are simply the free and open source version of the proprietary, for-profit permaculture program, without the misogynistic, capitalistic personality cult permaculture is bogged down with.

Killjoy goes on:

Primitivists have done a good job of exploring the problems of civilization, and for this we commend them. But, on the whole, their critique is un-nuanced.

This isn't a very good critique of the anprim critique considering anarcho-primitivists have written troves and troves of theory that picks apart every form of authority that arises from the industrial world, while Post-Civ is nothing more than 2 short blog posts filled with strawman attacks seemingly informed by silly 'return to monk' memes made by communists to attack and smear anti-civs.

Killjoy continues:

What’s more, the societal structure they envision, tribalism (note that what our society’s view of what tribalism is is mostly based on faulty, euro-centric anthropology), can be socially conservative: what many tribes lacked in codified law they made up for with rigid “customs,” and one generation is born into the near-exact way of life as their predecessors.

Again, anarcho-primitivism's willingness to explore and analyze various indigenous tribes and bands both living and dead, and engage with these cultures to outline how they differ from the industrial model is not the same as anarcho-primitivism aiming to enforce a program for people to follow. It's not a world-building manifesto like communism is. There's nothing wrong with learning from indigenous cultures and adapting their methods in your own life - especially the anarchistic ones. Killjoy concludes:

We cannot, en masse, return to a pre-civilized way of life. And honestly, most of us don’t want to. We refuse a blanket rejection of everything that civilization has brought us. We need to look forward, not backwards.

Killjoy is describing anarcho-primitivism as it's described by all the notable anprims, while rejecting a straw-stuffed perversion of anarcho-primitivism built by (largely communist) internet trolls. She wraps up with this line:

We are not primitivists.

That's fine and dandy, I'm also a green anarchist that doesn't identify as a primitivist, but Killjoy really hasn't explained how Post-Civ differs in any substantial way from anarcho-primitivism. The only difference in this whole text I can identify is they propose proprietary 'permaculture' courses created by white men instead of the indigenous food forests permaculture was inspired by, and claims to be open to theoretical sustainable, non-extractive 'technologies' that are really no different than the tools anprims readily embrace.