In small groups, where everyone knows each other, communism works very well. Everyone working towards a single goal in a tribe or commune that agrees with the end result and the process can live happy fulfilled lives.
In larger populations, communism begins to fall apart because people become more individualistic in their thinking. The person who lives long distances away from you has no interest or stake in your well-being, so they are apt to live their lives to better themselves.
Which leads the larger community to need a powerful leadership to keep everyone focused on the same goals. The problem with that is the implementation of that power has to be enforced by force and threat of violence.
It also puts the power of focus into the hands of a small like-minded group. Which ALWAYS leads to a totalitarian government, and once a government breeches the totalitarian barrier, the people of that community become abused and down-trodden. Which leads them to a depressed standard of living and poverty. Everyone is equal, but poor.
Communism, or the idea behind it, in and of itself isn't bad, but it can never work with large scale human behavior. People in large groups cannot cooperate unless they actually know everyone in the group.