Agreed, of the many mistakes she made in 2016, VP was a biggie. I loved Warren for that slot though I wonder if it would have moved the needle.
Clinton's loss in 2016 was by such a narrow margin that virtually any major storyline you can point to (Comey's BS announcement right before the election, horrible VP pick, Russian interference, Bernie bros, etc. etc.) probably could have made the difference. But man, picking Warren would have been fantastic.