I don't know if this post was intended to be a reply to me or not, since I wasn't talking about Biden at all, but I'll have a go at it:
I think you're right, and that a Dem candidate who actually quacked like a duck consistently would perform better, but party leadership, rightly or wrongly, seems to be banking on keeping their current voters and trying to entice disaffected GOP voters (read: women), particularly in purple states, to either stay home (I hate both of them i'm not going) or vote Dem in a "at least he's not like Bernie, but maybe I can have healthcare again" sense. I live in Missouri, and my neighborhood had conservative grandmas out canvasing for ballot initiatives on the abortion issue for the first time since moving here, so I'll allow that they might be on to something, even if I don't agree with the tactic.
EDIT: to clarify, they were trying to put a ballot initiative to add abortion as a right to the Missouri constitution