I agree with the analysis of Biden being an unwinnable candidate, but I really think the stain that he’s put on the Democratic party is too deep now to convince the critical portion you identify as needing to come back in time. You’d have to see a near-unified front of popular DNC figures (read: Obama), respected social democrats (Bernie, Warren), party leaders, mainstream media sources (primarily MSNBC and CNN) and most of congress providing rebukes of positions and stances they’ve been vehemently screaming about for 7 months at this rate while directly throwing Biden under the bus in an attempt to pin all of this on Biden. Also many of these people have provided direct condemnations of the people they need to build their ground game. They’re trying to build their ground game through hiring- I don’t think this will work.
I see neither the party will (at the DNC level- they seem happily delusional that this will either all blow over or people will fall in line; they don’t understand this is a turnout battle), it’s main messaging apparatus (MSNBC, CNN), nor its elected representatives really even being willing to go along with the replacement plan. The only hope I think democrats have is Biden dying (which you’ve also identified). I additionally think he’s about poisoned electoral politics as the primary societal vehicle of change to a large contingent of millennials and an even larger portion of Gen Z.
China is subsidizing the transition away from fossil fuels which greatly accelerate climate change and if not taken seriously immediately will lead to the deaths of tens of not hundreds of millions in the next few decades. The speed at which this transition occurs is vital in saving human lives and preventing infrastructure losses previously unfathomable. Their actions towards green energy adoption both domestically and abroad are one of the few things that provide any sense of hope about a better renewable future.
On the other hand: BUT AT WHAT COST