Ideally, an actual Leftist and not a Neoliberal geriatric centrist like Biden would get the nomination. That's why so many DNC supporters were upset with Bernie's campaign not securing the nomination.
But, despite Biden's flaws, he's still better than any GOP candidate easily. With a GOP President, we'd still have many of the same exact issues(mass shootings, inflation, crime, shaky economy, threats of war, etc.) that we have now but with the added dosage of an empowered fascist government that's already banning affirmative action and other tangibles with Trump's help.
So, if my ideal candidate doesn't make the nomination and I'm stuck between Biden and Trump/DeSantis/Vivek/Haley/Christie/Pence/Cruz, etc., I'm going with Biden. Not because he's ideal but because the GOP is just that trash and they've been pushing for a full scale fascist takeover for quite a while and Trump will accelerate that agenda since he already brags about how the people he selected in the Supreme Court are doing away with tangibles.
And 3rd Party/Independent candidates usually have zero chances of actually getting elected and the only one with a shot is RJK Jr. who's a QAnon/Anti-Vax/Anti-woke shill masquerading as a Leftist.
So, to me, a vote for Biden isn't even necessarily supporting him but it's just realizing that the GOP is gutter trash and there's too many Boomer/Religious/Blue Dog Democrats who find Biden to be a safer option than an actual Leftist who will fight for democratic socialism or at least a semblance of it.