Purpously forking the discussion here, since it's two separate points and I don't want one to overshadow the other.

Capitalism theory is ex-post, while communism theory is ex-ante.

Or to put it differenlty: Capitalism just happens while communism is a design.

Every single society that has ever existed spontaneously forms hirarchies.

So capitalism theory is about how to mitigate or exploit (depending on what side of the discussion the theorist is on) these hirarchies.

Communist theory instead is like a what-if-fanfiction to capitalism. What if nobody wants power? What if nobody wants an advantage?

There are essentially two ways communist theorists go. Either they split the world into bourgeoisie vs proletariat, believing that they are two separate species of humans and only the bourgeuisie wants hirarchy, so if they kill them everyone else has no wish to ever have an advantage over others, which is obviously flawed thinking. The proletariat is not in power because they can't, not because they wouldn't want to.

The other option is to proclaim the "dictatorship of the proletariat" (a term coined by Marx and Engels, which I guess, according to your definition aren't real communists either then), embrace hirarchies and have a central instance that governs and enforces their view of communism.

There's a simple reason why hirarchies emerge. People aren't identical. There's always someone who is more intelligent, has more knowledge/experience, is more charismatic, speaks/writes better, can naturally get people to follow them. Boom, there's a hirarchy.

And if that person is consistently the person others turn to, this hirarchy becomes solidified.