Communism like all utopian ideologies is founded on a wrong-headed assumption about humans. We are not blank slates that can be reprogrammed to "get with the programme".
We have an innate nature with complex intuitions about fairness and autonomy.
This is why every attempt at applying Marxism in the real world requires the imposition of a police state and a system of public shaming and informants. The weakening or even dissolution of family relationships is essential so that the new comradeship can demand universal loyalty. Any degree of punishment and state murder is justified if only the last vestiges of reactionary opposition or dissent can be eradicated then utopia will prevail.
It is a failed philosophy. It is not that we just haven't tried the right sort of Marxism yet. That much ought to be clear.