The problem isn't communism per se, but communism forcibly imposed.

More precisely, the problem is that communism is the superior system to the degree that it's egalitarian - that it eliminates the ruling class and instead treats all citizens equally - and the forcible imposition of communism immediately destroys that, since it presumes that those carrying out the forcible imposition rightfully possess the authority to do so, and thereby simply establishes them as a new ruling class.

Communism should be the goal, but in order to actually fulfill its potential, it MUST be voluntarily adopted by the people rather than forcibly imposed.