Kamala can't carry the ticket, even with a favorable VP.
The Democratic party will ruin the political careers of their rising stars like Pritzker, Whitmer, Newsom, etc. by requiring them to finish the Biden Administration's efforts.
Stand strong by Joe until he wins the election and then allow Kamala to formally take over when they're in the WH. Moving the deck chairs around now isn't going to jump start Dem voters and will cause divides over power dynamics within the party.
Dems don't truly care about Bidens ability to lead, they care about how Repubs view him and them.