This isn't specific to Warren, but one thing I was frustrated with in general about the 2020 Dem Primaries is how much of the debate was spent talking about things that, politically, were not feasible. For instance, it seemed like practically every TV debate had 30 minutes on health care, with extensive discussions about Medicare for All which, frankly, would have never happened even had Warren or Sanders won the primary and general elections. Much discussion on immigration as well, including a lot of discussion about amnesty. Put another way, much of the discussion that was centered around stuff that would have never had the requisite support in the Legislative branch to pass anyway. I'm just trying to imagine the message that the average voter who watched the debate (or the two minute blurb the next morning on the local news) got out of that, and how beneficial it was.
There's a lot of reasons why Biden ended up winning the primary, but one of the more underrated reasons IMO is, frankly, he came across a lot more realisitic about what could be accomplished when he was campaigning. And that means a lot to parts of the Democratic Party, particular with AA voters who are not predisposed to take flyers on risky candidates.
In terms of your comments about how Warren should retailor herself, one of the lessons that needs to be taken after VA/NJ (frankly, overdue to be taken) is that it's not good enough to put out some good policy and just hope that people go onto the website.... they all need to be out campaigning on this stuff. And not just in the suburbs and urban areas, they need to get out into more hostile territory to try and persuade. There's this tendency in politics (on both sides) to just look at the color of the county and determine whether it's worth spending time in a place accordingly, but the Dem vote you win in a Huron County counts the same as one you win in Wayne County..... if you can decrease the margin you lose in red counties, you can win a lot more statewide elections that way than you do getting your doors blown in.