Okay, I'm sincerely going to try to help you here. I've been pretty inflammatory in this thread, because, frankly, I'm pissed. But this is honest to god advice:
Forget that I am a member of a progressive forum and imagine I'm some voting schlub in the midwest or in Florida or wherever the hell else.
Imagine I, as this hypothetical person, voted for Trump in 2016 because I really did think that the country would be better if a businessman outsider came in and changed up a political order that had left my community in poverty. Imagine I saw the constant hair pulling and shirt wringing from the Democrats, saw Pelosi's poorly staged political theater, saw the clumsy and hasty impeachment trials, and thought to myself, "Okay, maybe they really don't like this guy. Maybe they're afraid of Trump, and maybe he's getting things done after all!" (To be clear, I think this is a profoundly stupid position, but one I hear echoed by people who aren't hardcore MAGA hat wearing folks, but just working people who are low information, well intentioned, and convinced [for good reason] that traditional politicians like Joe Biden don't actually give a shit about them).
So say I'm this person, and say that I'm not exactly foaming at the mouth with hatred for Trump. Say I'm in a take it or leave it position with the guy. Like, the economy seems to be doing better, but I think he spends too much time tweeting or whatever. But if a better choice came along, I'd consider it.
Now
Without just yelling about Trump and how big of a threat he is, talk to me like a human being and convince me that Biden is a better choice for me personally. Tell me why, if my life isn't measurably better or worse under Trump, I should be bothered to vote for a man closely tied to an administration that didn't necessarily help me either but who has said things like he wants to take my grandmother's social security away or who I've seen on TV being weird with little girls.
My advice, at the end of all of that hypothetical, is that you need to come up with something better than "Getting rid of Trump," because like it or not, there are a lot of people in this country who don't hate Trump as much as you do, for whatever reason, and they do vote. And if you put a nothing candidate like Biden on stage with Trump and the best he can offer is, "I'm not him," then you're screwed. That's all there is to it.
Edit: Just to be completely clear here: If you honestly think that a right-leaning moderate like Joe is the best bet to oust Trump, then this is what being a center of the aisle person looks like. You can't say that the centrist is the best bet and then refuse to reach out to people who voted for Trump. So you need to figure out how to do that successfully or you're going to see a repeat of '16. Remember Hillary's 'basket of deplorables' goof? Imagine framing Trump voters as bad people and still getting them to vote for Biden.
Best of luck to y'all with this.