The way to tell MAGA propagandists from real lefitst activists is that propaganda will ignore primaries and local elections. General elections in America are for forming coalitions, not rejecting them.
Anyone making memes telling you not to form a coalition against MAGA is working to further the goals of MAGA.
Don't make me defend the US voting system but that is not how it works. Primaries exist and that's where voters make the case for a specific person. The large, general, national elections are for forming coalitions and compromising. This is what we do to decide who gets power instead of physically fighting. There will never, ever be a time when a single candidate is the ideal choice for a majority of Americans. Compromise is a core tenant of democracy and by definition it means nobody gets everything they want.
And while we're on the topic, 99% of leftists understand this. Anyone telling you "voting doesn't matter" or that "both candidates are the same" is just trying to reverse the progress that's already been made.