There's a lot of confusion in these comments regarding Marxist theory, presumably from people who haven't actually engaged with the source material, so I want to clarify something I see repeated frequently in this thread with little pushback. The Marxist theory of the State is not the same as the Anarchist, nor the liberal. Marx defined the State as a tool of class oppression.

The reason I state this is because there's a confused notion that Marxists think there should be

1. An unaccountable Vanguard
2. The Vanguard does stuff. At a certain arbitrary point the Vanguard dissolves and society embraces full horizontalism

I'll address these in order. First, the Vanguard is in no-way meant to be unaccountable, nor a small group of elites, but the most politically active, practiced, and experienced among the proletariat elected by the rest of the proletariat. The concept of the "Mass Line" is crucial to Marxist theory, that is, the insepperability of the Vanguard from the masses. If this line is broken, the Vanguard loses legitimacy and ceases to be effective, whether it falls into Tailism or Commandism. These tendencies must be fought daily, and don't simply vanish by decree.

Secondly, the basis for Marxian Communism is the developmental trends of Capitalism. Markets start highly decentralized, but gradually the better Capitalists outcompete and grow, and as they grow they must develop new methods of accounting and planning. Capital concentrates in fewer and fewer hands, yet socialization increases as these conglomerations begin to reach monstrous heights and require incredibly complex planning. The development of such methods and tools is the real, scientific foundation of Public Ownership and Central Planning.

Continuing, once the Proletariat takes control and creates a Proletarian State, the Proletariat, the more experienced among them the Vanguard, gradually wrests from the bourgeoisie their Capital with respect to that industries and sectors that have sufficiently developed. This process continues until all Capital has been folded into the Public Sector, at which point laws meant for restraining the bourgeoisie begin to become superfluous and "die out." The Vanguard doesn't "dissolve" or "cede power," but itself as a concept also dies out, as over time new methods of planning and infrastructure make its role more superfluous. Classes in general are abolished once all property is in the Public Sector, and as such the State no longer exists either, as there isn't a class to oppress.

This is why Marxists say the State "withers away." It isn't about demolishing itself, but that Marx and Engels had a particular vision of what the State even is, and why they said it could not be abolished overnight.

Hope that helped! As a side note, asking this on Lemmy.world, an anti-Marxist instance, is only ever going to get you answers biased in that direction. I suggest asking on other instances as well to get a more complete view.