Voters need to force Democrats to the Left. The Democrats need to get people to vote. Those are two related but different issues.
Democrats wont have an issue with turnout until Trump is gone. That's the period I'm talking about. They can trot almost anyone up there right now and be competitive. It was a unique case but look at Doug Jones (who I haven't heard from since he got elected). He's not a progressive in any way whatsoever.
It's up to the party and who they push in primaries and where they allocate their funds to pull the voters to the left. AOC won her primary and Obama didn't endorse her in his first wave of endorsements. He may eventually, but there was no reason not to put his stamp of approval on her other than a hesitation to bring the party further left. That's indicative of a lack of long term foresight