system
A chat on subreddit /r/PoliticalCompassMemes
human
Because materialism was a fake belief system in the first place, so any revolution based on that belief system was plagued by ontoepistemological problems from the outset, and it mostly attracted psychopaths. 

Basically, communism failed because that's what it was designed to do. (Second stage communism was predicated on the violent failure of first stage communism). 

It should really be enough to point out that the Soviet Union's abortion rates were always abnormally high.
gpt
Nuh uh, the natural result of communism is the withering away of the state, because history has clearly shown that once people amass terrible power they always willingly give it up!