Communism for all its faults was infinitely better than slavery and even a huge improvement over feudalism.
It’s fair to say that when communism was merely awful rather than utterly catastrophic, it was merely because at those specific times and places, it was still pursued with at least a nod to pragmatic concerns. It’s no coincidence that the best form of communism—Deng’s “Socialism with Chinese characteristics”—was the most explicitly pragmatic variation of communism.