I said this in 2016 and I said it in 2020 and I'll say it again:
If you don't like the fact that the leftmost candidate of the two major parties isn't left enough, the solution is neither to refuse to vote, nor to "send a message" by voting third party. Both result in an advantage to the rightmost candidate.
The solution is, vote for the guy that's not quite good enough, and then lean on him hard.
Biden has moved farther to the left than any president since Roosevelt. Yes. He's gotten more of our agenda done than Clinton or Obama. And there's many things he's tried to do that the right wingers in Congress or in the Supreme Court have stopped him from doing. He's also moved farther to the left than any president I know of when you look at his whole career; at one point he was Liberal Lite, "moderate", pro-corporation, etc... and it seems he learned from it. He changed. So we're dealing with a guy who is capable of moving left, has done so, and could be asked to go farther.
The other candidate literally wants to become a dictator, eliminate freedom of the press, and spend our tax dollars persecuting his "enemies."
Do I like the fact that Biden is supporting Israel militarily when they have caused such an enormous and horrible death toll in Gaza? No. But we have treaties with Israel and we can't easily break them. Meanwhile we have actually seen him call Netanyahu out. Including saying basically "You keep this up and no one will be your friend", implying that he is threatening to withdraw support. Trump, meanwhile, is cheerfully Islamophobic and would happily murder every single Palestinian. You care about Palestine, there is only one legitimate choice. I'm sorry, I know you want to believe there are multiple moral options you can take, but there is really only one. In the US's winner-take-all first-past-the-post no ranked choice system, the guy who gets 51% of the vote and the guy who gets 90% of the vote are exactly the same.
Look, we can win this. The right's abortion bans are wildly unpopular; many people will be voting to try to restore the right to control our own bodies. Republican support skews older, but in four years millennials didn't magically reach a point of comfortable status quo where they're likely to start voting Republican; instead Republicans have doubled down on the crazy. Anti-maskers and ant-vaxxers, who are likely Republicans, are much more likely to have died of COVID than the reality-based community on the left, since Biden won by 7 million votes 4 years ago.
But Trump will do everything in his power to cheat. We can't just win by 51%. We have to trounce him and as many Republicans at the ballot box as we can, because they have lost the plot. Even the best ones refuse to do anything to stop the spread of this evil-for-its-own-sake movement that wants queers, Jews, and Muslims dead, POC subservient, and women of all races securely under the thumb of men. We have to stop this movement by sending a message to politicians, "these are not winning ideologies. Embrace these ideologies because of the fanatic fringe, and you will lose." Most of them aren't true believers; they're pandering. The only way to stop the Republicans being pointlessly destructive is to make so many of them lose, the rest realize, shit, the grownups are back, we better start acting like politicians and not demagogues again.
And one of the best ways to do that is to make sure Biden wins by such a large margin even Trump can't cheat his way to victory. Because he's ready. He's promised, there will be violence if he loses. (There will also be violence if he wins, but it will be state violence against us. If he loses, there will be rioting white thugs in red states, but the federal government will still have both the power and the will to try to stop that.) He's going to pull every dirty trick in the book to win. The only way to stop him is to win overwhelmingly. Then we get four more years of relative safety, where if Clarence Thomas dies or gets arrested we get a young liberal judge in his place, and in that time, we can push the Democratic party farther to the left, because they'll know why they won. They'll know who voted for them, and why, and they'll move in that direction because they want to keep winning.
You cannot save Gaza by making sure Biden loses. That is actually the worst possible thing that could happen, in terms of anything any American could do. Netanyahu wants Trump to win because Trump will back him up no matter what he does to the Palestinians.
Voting is not about proving how moral you are and selecting the perfect candidate. Voting is about getting the best possible candidate out of what is usually a lackluster selection. But this time, the choice is, an old guy who's not as charismatic and shiny as we'd like and hasn't done as much as we want, vs, literally, a wanna be dictator with an agenda that's pure evil.