* 50 years or more

Not that I'm disagreeing with your thesis as applied to the modern day, but pre-Lyndon Johnson, the Democrats were the racist party. There was a massive sea change during the era of Nixon, when the Democrats decided after quite a bit of heated internal debate that they couldn't possibly stomach depending on the support of the segregationists, whatever the cost, and the Southern Strategy scooped all the for real lynch-mob enthusiasts all up for Nixon. Except for Carter's brief flirtation with actual human decency, which the US isn't okay with for some reason, the Democrats got accustomed to losing elections for quite a while, until Clinton decided to make a pact with the neoliberal bastards since all the actual progressives were so ground down into not-voting-land that they weren't even worth appealing to anymore. That worked and that set the tone which has continued to the modern day of slight steady progress under Democrats versus absolute naked fascism under the Republicans (accelerating year by year to its current breakneck pace.)

Side note, if you want to have your heart broke a little bit, read Hubert Humphrey's speech at the DNC in NINETEEN FUCKING FORTY EIGHT, where he calls out the Democratic party for their acceptance of racism:

My friends, to those who say that we are rushing this issue of civil rights, I say to them we are 172 years late. To those who say that this civil-rights program is an infringement on states’ rights, I say this: The time has arrived in America for the Democratic Party to get out of the shadow of states' rights and to walk forthrightly into the bright sunshine of human rights.

He was still around in 1968, in the literal bloody battle, inside and outside the convention hall, for what the Democrats were going to be. They never fulfilled their promise completely, and they still haven't, and that year it cost them the presidency, just like it did in 2016.

I say this 1,000% agreeing that Biden has represented a big step forward and accomplished some genuine impressive things, and that voting for him in November is an affirmative good thing and not just a way to prevent Trump's end of the world. But the Democrats had to be dragged kicking and screaming by their progressive wing into doing good things, just as they have to be now on Israel among some other issues.

The difference is that they can be dragged into good things, which is enough. And they've done pretty much all of the progress the country has made since 1976; I'll fully agree with you there.