Well, it is not anymore inherently hierarchical than a parliamentary monarchy or a republic. Communism is simply supposed to be workers seizing control at the means of production. What happens from there and how that revolution is organized is what makes it hierarchical and/or authoritarian. Turns out, its not so easy to consolidate complete control of every aspect of an entire economy and not become vulnerable to corruption and take-over by authoritarian bureaucrats. Imagine that. However, its is also not like the U.S. is not vulnerable to becoming an oligarchy either. I think Trump showed us that. This is why Democratic Socialism just makes the most practical sense: Checks and balances on the government and checks and balances on the economy. A democratic state managing an economy in the interests of those who actually build and maintain it, not just for the greatest benefit of the wealthy.