OK, but all of this is only relevant if you believe Biden in his current state is able to win against Trump. The people who want Biden out believe that Biden stands no chance.
it's looking increasingly difficult for the Democrats. Biden's not impressing people, the business with Israel is putting off some of his supporters, and they've left it very late to not have a Plan B. You'd think that any party running an 81-year-old candidate would have a fallback plan ready from the outset, or might anticipate difficulties and run a younger candidate in the first place, but apparently the Democratic Party doesn't look that far ahead.
They should have been building Harris up for the last 4 years instead of giving her shit issues Biden didn't want to deal with. They knew it was possible she'd be forced to lead the party, but they were just so singularly focused on Joe Biden like he was a regular president and his reputation was the only important thing to manage.