I can't agree with you. Now, I agree that Democrats didn't consider Bernie as seriously as some Progressives would have liked, but sadly (the argument I continue to have with my husband) Bernie would not be able to win a Presidential election. Americans are too anti-Semitic to vote for a Jewish President. One factor in Al Gore's 2000 loss, though people won't say it out loud, was their dislike for a "stereotypical" Jew.
Elizabeth Warren, proudly Progressive, was also not going to win the Presidential Election race in 2020. Again, American voters aren't yet willing to vote for a woman as President. Good grief, Hillary Clinton was superior to Trump in every way, but Americans invented reasons to hate her. Most were due to misogyny.
Remember that Joe Biden was losing primaries all over the place. He was not "the anointed" candidate until Clyburn pulled him ahead of the pack. Thank you, Jim Clyburn. I consider myself a Progressive, but I know that, except in specific areas, Progressives tend NOT to win. Ideology is great; it fires people up, but pragmatism wins races. You get nothing if you don't win. I hope you'll stay in the fold for one more cycle and help us win. If you're sad now...