It can't be understated how bad of a campaign Warren ran, and how poor of a presidential candidate she is. Leave her in the senate, where she can craft biils and nerd out all she wants. On the political stage she doesn't come off well. People don't care about plans or policy right now. They want help. The question is whether the guy in charge can give it, or whatever the next guy can. There is nothing intellectually impressive about Biden, nor has there ever been. But if voters trust he can fix this with a competent tone and TEAM...he wins.
Warren fires up parts of the base...ie the non black parts. But again, she didn't do shyt in the primaries. Didn't win her state. Nothing. She's certainly a calm, intelligent hand...something that could be needed at this time. But again, I'm just not sure I want her on that stage.