The reason why Rojava isn't anarchist is two-fold:
First, it was never intended to be anarchist. Rojava was intended to be democratic confederalist. Democratic confederalism is an ideology created by Abdullah Ocalan, the head of the PKK (which, prior to Ocalan's ideological shift was Marxist-Leninist), that was heavily inspired by the communalism of Murray Bookchin.
Communalism was an ideology Bookchin created after he broke with anarchism. He broke with anarchism because, after doing deeper reading into anarchist literature (or what anarchist literature was translated and available at the time), he realized that anarchism was opposed to direct democracy or majority rule.
You see, prior to this, Bookchin was a proponent of direct democracy of which he associated with anarchism. However, he faced criticism from anarchists contemporary to him like Bob Black and, after reading anarchist literature, realized that historical or classical anarchist writers disagreed with him as well.
Ocalan, while in prison, read Bookchin's works and furthermore realized that the Marxism basically has no political relevance anymore since the Soviet Union has fallen (which means no more Soviet funding or assistance). He creates his own ideology, democratic confederalism, which is literally just communalism but with essentialistic feminism attached to (seriously, read Ocalan's feminist work it's all icky essentialist drivel they need some Judith Butler up in there) and declares it the ideology of the PKK.
Second, Rojava isn't even communalist. Rojava, while nominally communalist, structurally wasn't. Structurally it's just a regular capitalist liberal democracy. And we can debate about what led to it being so benign. For instance, we can point out how PKK tried to top-down impose communalism on everyone (which was the opposite of what Bookchin suggested). We can point out how the pressures of the Syrian Civil War might have forced the PKK to be more reconciliatory towards local authorities than it should've been. It might be that the PKK was too nationalist (the goals of the PKK since the beginning was an independent Kurdistan). We might even suggest that communalism itself is predisposed to the kinds of authoritarianism exhibited by Rojava and that communalism is just a failure.
However, let's get into the specifics of how it works. Rojava is a standard federal democracy with an unelected executive council that comprises the party elite. It is structured as follows: at the top you have the unelected executive council. This council commands the entirety of Rojava and can make decisions without the consent of any of the democratic bodies under it. This is the authority that established ties with the Assadist regime and promised to integrated the SDF into the SAA, thereby throwing away all of the gains of the revolution.
Below the executive council you have the legislative council or the parliament. It is exactly as you'd expect. It is a body with seats consisting of different percentages of the political party which then elect a prime minister who is accountable to the parliament. The parliament also makes decisions that effect the entire country however these decisions can be vetoed by the executive council. This is how a majority of European democracies function (although democracies typically don't have an executive council that governs the entire country unilaterally).
Below that you have the cantons which make local, small-scale decisions. They can't do anything radical, for instance they can't have different agreements with different foreign polities like the Turks or other rebels, and so in that regard they are not autonomous. They are about as autonomous as autonomous regions in Spain, that is to say not at all. They're akin to provinces or states if you're from the US. Below that you have communes who make even more localized or small-scale decisions and below that you have neighborhood councils.
As you can see, Rojava fails to be even communalist. By its structure, it's just a pseudo-liberal democracy.
Here's why Rojava is capitalist. First, Article 41 of its constitution protects the right to private property. Indeed, Rojava has actually not removed any of the properties owned by capitalists and corporations prior to the Civil War. It has actually maintained them. Furthermore, the economy of Rojava itself is thoroughly capitalist subsisting off of small capitalism, the selling of oil, and black markets. Cooperatives are only a very marginal part of its economy and the administrative body which is supposed to fund them doesn't for some reason (likely out of nepotism). Even then, cooperatives are capitalist businesses and are governed directly by the government (by law they can even remove the owners) so they aren't autonomous either.
There is more info in this regard here:
It has interviews with PKK and SDF members as well who are a part of the government.