What do I need to move on from or do about it?
Stop playing the blame game and do literally anything. You're projecting your own personal inaction and frustration onto progressives.
In a constitutional crisis, while the last shred of democracy is at stake, do you simply vote your way out of the mess?
If Democrats could've budged even a little bit to the left, they would've won and stopped Trump. But they couldn't. They also couldn't hold primaries before the presidential election.
You don't need to be a psychic with a crystal ball to determine that Kamala couldn't win, especially not with her strategy of shifting to the right and appealing to voters that literally don't exist.
Democrats spent more energy systematically suing third-parties off the ballot than attracting the voters they were so afraid of losing to third-parties.