Voting for Biden/Dems isn’t much of a plan either, it’s just stalling. But you need to stall for something, you need something that you are buying time for.
In regard to third parties, my country has a different system, a parliamentary one (technically semi-presidential, but for the purposes of the topic, it’s parliamentary), but nevertheless, up until recently we had 2 major parties, and so far only one of the 2 ever won an election, and all my life I’ve often heard the argument of “useful vote” (“voting for someone else is a waste of your vote”) as a justification to vote for one of them, even from journalists and pundits. But the far right, for one reason or another, simply didn’t care about a “useful vote”, and just voted for who they wanted; that is why in our last elections, and for the first time since we’ve had elections, everyone was now talking about 3 choices for a useful vote.
I know it’s a different system, but the point of the story is that you are engaging in a self-fulfilling prophecy. Neither democrats nor republicans will ever want to change the system because it will hurt them. Voting blue instead of red is a stalling tactic to stop/delay the fascists, but it doesn’t actually solve anything.
I think this is it.
The historians I know of actually seem to lean quite left of the average person; it’s the light hobbieists, who are often more interested in the aesthetics/surface stuff, who seem to fall victim to the alt-right stuff.