The "heads need to roll" point is one we can use. Any upper-level Democrat who's had access to Biden and lied about his condition should resign. They're the one saying the stakes couldn't be higher, and they lie about how inept their candidate is? And that's not even getting into the issue of having an inept day-to-day president.
Rank-and-file Dems won't get behind "Biden is a war criminal who should be arrested and turned over to the ICC." This is the type of idea they will get behind, and it can be used to eventually bring some to of the left of the party.
Clinton has been wildly unpopular for the past 30 years. Biden may have been uncomfortably pro-segregation, been best friends with Storm Thurmond, and help usher in the neoliberal order, but he was veey popular as the Obama's VP, and that image has carried him a long way since 2009. Hillary massively fails the vibe check.
Yep, Biden is basically riding Obama's coattails even today as President and everyone just overlooks that he was the racist centrist there to placate the "moderates"
Biden is way worse than Hillary
At least Hillary pretends to care about reproductive rights
Somehow the democratic nominee has only gotten worse and worse every cycle