Take Biden out? Get behind him? Time is running out, and I think the absolute worst course of action would be to continue what it looks like they've been doing for a fair bit now...which is cover for him, and let public perception of DNC leadership continue to erode.
There needs to be some decisive action taken, and taken very soon. And since one of those decisions relies on Biden, and his team, to agree to be "taken out"... With Biden certainly not appearing to be on board with that. THEN, I think they need to end all the speculation, and get back to fully backing him. But more importantly, enlisting Harris, Newsome, Whitmer, Obamas, etc... to become HEAVILY involved in general campaigning for down ticket races.
Biden is not going to beat Trump. Unless Trump finally figures out how to hang himself. Practically though, Trump is going to win in November. Even if Biden backed out today, I think Harris or whoever the replacement would be, wouldn't have time to clean up the mess and rally everyone to beat Trump.
So, get behind him. Hide him. Be strategic and use him however he is most effective. But GET TO WORK, with more believable and potentially popular campaigners, and salvage as much of the House and Senate as possible.
The silver lining, if they're effective at saving one or both of them, is having a split White House and Congress "should" limit the damage Trump can do in 4 years. And if this whole Biden thing has resolved the party, at all, to take the POTUS candidacy more seriously, and they actually work to prop up a couple good candidates... The damage Trump will end up doing to the GOP's image over the next 4 years could set the DNC party up well in 2026, 2028, and forward.
They're losing the Oval Office no matter what, at this point. As an Independent...I really, really, really hope they figure out how to avoid losing the Senate and House as well. That should be what matters most right now.