People will often say that Stalin's USSR was not communist, but was rather in a pre-communist phase. In the USSR this stage was known as the dictatorship of the proletariat, which according to Lenin, would eventually fade allowing a state-less, class-less society to flourish. Obviously they never got to that stage, but honestly even arguing this is semantics. Communism vs precommunism is a real time waster of a political debate, but I've never heard anyone describe any stage of the USSR as "capitalist". Perhaps state capitalism, if you really want to stretch that definition, but that's still a very different thing.

Generally lefties will distance themselves from Stalinism and Maoism by describing those forms as "authoritarian socialism", as opposed to "libertarian socialist" ideologies like what they had in socialist Catalonia, or Anarcho Communism as it's described in The Conquest of Bread.