Unfortunately, this explanation isn't cynical-- rather, it's rational. The problem with Communism and other idealist economic/political systems (like Anarcho-Capitalism) is that humans are fallible.

A Communist government must have total control of every individual within its area of influence, and thus must have leadership which never falters and serves only for the good of the society. It must also be subject to no outside influence, and therefore must be totally self-sufficient and totally isolated.

On top of this, no member of society can be granted anything they do not strictly need, and every member must give to society everything they are able.

The result of all this together in previous times was a starving, unhappy society, run by greedy, corrupt, sociopaths who murdered anyone who disagreed with them, and were quick to commit deliberate genocide- having already killed their more naive compatriots who lead the revolution in the first place.

In the future, when the entire world is run and cared for solely by robots and computers, we may eventually see a time when capitalism falls by the wayside and is replaced by communism once and for all.

However, as long as a human being must be the one in charge, or humans are required to perform labor for the sake of society, communism fundamentally cannot work.

that doesnt work for their thought experiment
Communism would work where humanity was eusocial for instance and mot a tournament species.
Some thoeries call gor intentional genetic engineering, i believe engels called for that spefically mass murder of those who cannot be socialist.
And selectively breeding and culling people umtil communism works is a possibility