I think that even the people who are just as bad as you say are also part of the Democratic coalition simply because both they and I will be voting for Kamala Harris in November, although they will be doing it while complaining a lot. I’ll be complaining a little because I’m never going to support any candidate 100% but my ideal candidate would still be a centrist Democrat.
With that said, I’m not sure how long this coalition will hold together because I would rather vote for a centrist Republican than for a leftist. Right now the Republican party is the one dominated by its extremists but if they return towards the center (Trump won’t live forever) and the Democrats shift left, a lot of liberals will be reconsidering their political alliances.