Answer:
Communism on paper is good but in practice.. meh not really.
Step-by-step explanation:
The Soviet Union, Vietnam, China, and Cuba advocate Capitalist policies because they can make more money off of that. True Communism, such as Marxism would be unrealistically hard to pull off in actual society. This means no one should move up the social ladder as that would go against the ideals of Communism. People are naturally ambitious, which would be a problem with the economics of true Communism.