Politics in general just got so corrupted that there's no faith in the future they pretend is possible.
Once upon a time politicians actually laid out a view of what they were going to do and how it was going to make a remarkable improvement in your quality of life. There hasn't been a serious improvement in any of our lives for what seems like decades. The promise of an infinitely developing post-industrial society where things will get cheaper and humanity will grow? It doesn't exist. Liberalism has universally failed in most places, they just fight about the flavor of failure. The post cold war era "end of history" has completely ended and we're in uncharted waters.
But liberals still hold the reins of power, even though they've basically lost their mandate, because the democratic system can't really punish them for it. For maximal appeal, most parties have just become this big tent of bitching that ignores real material issues facing society, and the legal system in place prevents even parties that get elected with a mandate from making sweeping changes to a system that clearly is dysfunctional. The migration waves made it worse because it very clearly debases the quality of life of our society even worse than was already happening and the liberal left allied with the migrants on principal.
Leftism still exists(as in, socialist AOC/Bernie Sanders types), but the Clinton/Obama world has completely fucking died. The inside of the Democratic party if you look at it deeply reflects this, the vast majority of the youth and nonwhites did not support Hillary, Biden, or Kamala because they reflected a fake Obama politic instead of meaningful change.