I mean, I feel like it is quite fair to blame the people who voted for Trump for Harris's loss tbh. I don't really buy the "the dems would win if they didn't just refuse to try to win over conservatives and instead promised to go all-in on progressive policy that I've seen lately. I wish we got more progressive policy too, but it's not like they don't have any idea what people want, they have whole teams of people whose job it is to figure out that kind of thing. If promising some more progressive policy was a clear winner, why wouldn't they do it? The answer I generally see implied or stated is that the dem establishment doesn't want that policy, but that isn't really an adequate explanation, because politicians are perfectly familiar with dishonesty. If supporting some progressive policy they didn't like would win them power, they'd just promise it and then just not do that thing upon getting elected. It's happened for state and congressional races before, so it's not like that's never been thought of.
I don't think Harris's loss is down to refusing to say the right words to inspire her base or anything like that, it's down to the fact that, somehow, Trump is very good at inspiring his. She gave it a decent shot, but it's very hard to win an election against a massive cult of personality. He, and the people that support him, are the problem here.