Speaking in over-generalized strokes, most Anarchists want some form of horizontal network of Communes. The Marxist critique is that this doesn't get rid of class, it makes everyone a petite-bourgeois owner of their commune's MoP, and further this isn't a natural progression from Capitalism like (Marxian) Socialism is.

Marx's core critique of past Socialism, such as the Owenites, is trying to design an ideal society in a lab, and create it, rather than continue to build up society and erase contradictions gradually. Capitalism centralizes, because production becomes incredibly expansive and complicated, ergo he believed it would eventually be necessary for the government to take over just to run it, and that this government must be of the workers to properly handle it as Capitalists outlive their usefulness.

I recommend checking out my introductory Marxist-Leninist reading list, at least the first few sections, for more on this.