All the iterations of Communism as enacted in the world with its various flavors (not as described by Marx himself, which I have less issue with) tend to have fundamental structural power issues that cannot be resolved, and inevitably become authoritarian and eventually corrupt. Relying on who is steering the boat to have a positive outcome means that even if lucky enough to get a good person, it's easy enough to replace them with a bad actor.

History has clearly shown centralized power cannot be wrangled reliably, which I think strongly necessitates the need for decentralizing power at a fundamental level to prevent the failings of the past.

I won't dispute that some communist dictatorships did result in some benefits to the poor and disadvantaged, but at a needlessly great cost to liberties and innocent lives. I don't personally agree with the Michael Parenti viewpoint that we shouldn't be so harsh on previous communist regimes because of those gains. I think in the end, Capitalism and Leninism, Trotskyism, Maoism, etc. are ultimately horrific for the soul, and we have better solutions that mitigate the possibility of those extreme negatives.