The ratchet isn’t gonna turn the other way until the problem of money in politics is dealt with. Until then there won’t be a real progressive candidate to rally around as in the case of Bernie they get pushed back against by the donors and the rest of the party. I do think there are some problems with people not wanting to unite under one candidate but we’re not even really at the point where that’s the main problem as the bigger problem is donors and the establishment of the Democratic party.
No one in government except the few progressive Democrats who are routinely demonized and belittled by the rest of the party. The only way I see it happening is if Bernie or someone like him can pull a Trump and win the presidency and completely overhaul the party.