You said it yourself: it’s a duopoly. By your vote you have the power to nudge the outcome toward one of two possibilities.
More options would be fantastic, but that’s not the system we live in. The current options are fascism or not-fascism. You support 3rd parties? Then vote for whichever party has the best shot at not-fascism… cuz if fascism wins, 3rds are fucked right along with everyone else.
In your case, voting Trump, voting 3rd, or not voting at all are all just throwing in the towel. Fascism won! No point in fighting it; just bend over and take whatever comes next.
Biden may not be your cup of tea, but a vote for him is a vote to keep the fascists out of power - for you that’s a vote for more time. Right now our system won’t allow a 3rd to win due to the power accumulated by the big two; but it’s still malleable. Ranked Choice is getting onto more and more people’s radar, gaining popularity, and making its way into more and more states. RCV is your golden ticket to getting a 3rd in office - people need to be comfortable with voting for a 3rd without risking the ‘other guy’ taking power. And our system IS moving that direction.
Fascist victory and we can kiss RCV goodbye, along with most of our rights and any possibility for 3rd party to come out on top for a very, VERY long time.
Could it be better? Yes. Should it be better? Abso-fucking-lutely. But the best result possible in our shitty reality for 3rds and everyone who isn’t a Nazi is for the fascists to lose, and for that to happen, you need to vote blue.