With all due respect, that strategy got us fascism.

That argument is obviously false. We, people to the left of Republican voters, have been losing elections and Democrats since Clinton have been moving right as a result.

Apparently not, because socialsts/progressives/leftists are lazy, good-for-nothings who are simultaneously powerful enough to swing elections, but too inconsequential to talk about their issues or court their votes.

Of course we need more than just leftists to vote. We need to demonstrate a leftist voter block was part of what got Democratic candidates into office. So the Democrats feel they have voters to cover the ones on the right they think they could lose by shifting left.

In other words, maybe these vaunted “centrists”/liberals should’ve stepped up to stop fascism.

Yes. There can be more than one lesson to learn from an election. Democrats fucking up more than us doesn't mean we don't have a lesson to learn too. Obviously Democrats have to do better. But if they win without leftists when they do run a better candidate, they aren't going to shift left. They'll think they've hit the sweet spot and stay put on the political spectrum.