None of what you're saying here is "wrong," but this doesn't matter. The people you're talking about are either sure-fire Biden voters, or at best, people who might not vote. The thing is that this will not make those of them who might not vote decide to vote, but much more importantly, these are not the people who are largely affected here. The issue with Presidential elections is the swing states. It's not about twitter liberals, but moderates in swing states. Biden wins by doing two things:
1) getting more support from the base (more of the base comes out to vote)
2) more independents/normies vote Dem rather than Rep
From that perspective, it doesn't seem to make a ton of sense. Biden's not exactly the darling of much of the base, sure, but he's proved significantly more popular than Harris. The same is true with independents/normies. With all that said, I'm still not confident in the Trump campaign strictly due to his negative popularity with a large proportion of the voter base. Still and all, I find it hard to view Harris as anything but a net-negative for Biden. I am and live among midwestern whites, and I definitely get the impression that the prospect of a Harris Presidency is worrying to a large portion of them.