Nobody is arguing to only vote and nothing else. You are literally strawmanning an argument out of nowhere. Not voting dem doesn't make a communist revolution magically happen and is in fact going to make it harder.
Republicans are significantly worse and with full power will be more likely to start going full fascist on minorities and vulnerable communities before Dems do.
It is a tactical vote to buy time while we organize a revolution.
Letting Republicans win isn't going to allow the revolution be easier to achieve. Republicans have been sliding right on the fascism scale at a frighteningly quick pace compared to democrats.
Remember the saying first they came for the communists? A communist revolution was not possible inside Nazi Germany, because fascism had more power and snuffed them out immediately. The same is going to happen to communists in the US with letting Republicans win, they are already paving the way by labeling democrats as communists.
This is a very dangerous game being played by letting Republicans win. It could let Dems become more progressive to try to win voters or it could shift them more to the right to get more voters, either way it guarantees the more fascist party more power.