Per Marxism-Leninism the Dictatorship Of The Proletariat is a necessary step on the way to Communism, not the actual Communism.

So whilst Communism cannot exist in a dictatorship, to get there one must go through a dictatorship and invariably nations that do so get stuck at the dictatorship stage and never reach Communism whilst calling themselves “Communist” as part of the propaganda that tries and maintain public support and misportray criticism of the regime as being “criticism of Communism” and “criticism of the Proletariat” (kinda like the Zionists, an even more evil regime, misportray criticism of their regime as criticism of those they claim to represent - the Jewish People) to keep the dictatorial structures going supposedly until Communism is reached, but as it’s never reached, in practice for as long as possible.