Leninism and Stalinism is every bit as bad as fascism. In fact they are practically the same thing. That why Stalin made a military invasion pact with Hitler against Poland.

They will never fight for policy that actually improves living conditions of the working class

You mean like social security, medicare, and the ACA?

thus their sole ‘popularity’ has to stem from people who think they will fight against fascism

This is backwards. Their unpopularity is because they aren't fighting nearly enough against fascism.