Fascinating read, Peter! My 2-cents is that the Democrats are perceived as the party of entitled liberals (I agree with David Brooks here). When Biden went to support some union it looks phony to everyone. (I didn't like his picking sides). When he slaps tariffs on China most people don't see how that affects them directly.
I didn't vote for Harris because of letting Israel use our bombs in their civil war. I understand I'm rare in that case, but I feel most people see Biden as a failure in the world--Afghanistan, Ukraine, Israel. Lots of people getting killed under his Presidency. The U.S. looks weak and ineffectual. Fact is, we didn't have two wars going under Trump.
The bottom line, as you point out, is that the Democrats, in trying to be something to everyone, become nothing to anyone.
Even a friend of mine who spent a month in PA trying to get out the vote lamented how the Democrats had pulled so much money from poor people who couldn't really afford campaign donations. I got 7 emails a day asking for money. Even AFTER the election.
In short, both Clinton and Harris share the same perception. One is condescending and the other is a hack. Oprah should have run ;)