Marxism attempts to have it both ways. It's perfectly valid for Marxists to conclude that there is no reason to have independent managers and capital owners who direct the processes of production, because a less free, more unkind society is produced this way (since labor is inseparable from the human beings who do it) and there are perfectly good alternatives to this state of affairs.
But in addition to this, most Marxists also take a more hard-nosed economic approach and give arguments regarding production - surplus value, exploitation, the productive process, inputs, etc, following the ideas of classical economics.
There seems to be a lot of tension between those. The latter makes control over production seem somewhat arbitrary (there is no obvious reason to assign control to any one productive input, although plenty of ideologies have been founded over the years to do just that, from physiocrats to capitalists to many socialists) and undercuts the former by removing us from discussions of liberty & moral philosophy and brings us into discussions of means of production and monetary values. So I am always uncomfortable there, it feels like we are handing capitalists ammunition or at least choosing poor ground to fight battles on.
The dedication to constant economic growth inherent with Marxist ideology is problematic, and only leads to tyranny.