Obama did it (kind of); he moved the party line to be policy oriented instead of stunts and cutthroat politics.
At the same time, he never gained a sufficient majority to enact his platform (in truth we're lucky we got the affordable care act). Biden ran into similar issues with what was technically a majority but that had weak votes (e.g. Manchin).
Honestly the problem is the Senate; Democrats just can't get past the threshold that would let them actually govern. So we get Democratic presidents that appear ineffective ... when really we just have a Senate that's broadly ineffective at doing anything that isn't center right.
A Promised Land by Obama is an extremely good book if you want to understand the modern democratic party. Obama did a lot to get the spark back but also was in a very difficult position.
It's a complicated issue in the United States because of the history. Lots of countries did slavery, but at the point the United States did it, science was starting to spark into its modern form and one idea that "seemed good at the time" was pursuing superior genes.
That ... went really really really sideways and basically became a justification for continued slavery on the premise that white people were just better and they were doing the inferior black people a favor. Basically while the rest of the world was going "maybe slavery isn't good" the US was like "slavery is the humane thing to do, because science!"
Even after shit like that gets disproven people still tend to believe some amount of it (look at the antivax movement). So, even after the slaves were freed, they and their children were looked down upon by the culture. Many black people remained uneducated, financially bankrupt, etc. The culture especially in the south fought really hard to keep it that way for a looonnngggggg time.
That kind of formed a counter culture of its own, the "gang" culture. Which isn't all that different from the counter culture you see that came from prohibition and the moonshiners and such ... basically outlaws fighting the man, looked down upon, etc
So basically there are several main US cultures, Northern East White, Midwestern White, West Coast White, Southern White, Black, and the Appalachian White/redneck culture that descends from a mix of the moonshine runners, rural farmers, coal miners, and white southern culture.
Black people of course have multiple cultures even within the US but it's all kind of lumped into this messy "black culture" thing. Some black people I've met love the black gangster with the gold chains imagery and hold it up as something great and the "true black culture", others see it as ridiculous and trashy.
Calling these other cultures white is also intellectually dishonest as the entire US is a melting pot and the cultures of those regions were not formed by a single skin color ... but I'm using "white" for the purposes of the contrast ...
Anyways, black people just kind of stand out so they're an easy target... and they have been targeted for a very long time fueled (at least in part) by that long ruled scientifically ridiculous idea that they're inferior.
Add in the extra spice that the Appalachian subculture is angry about being tied in with the other white cultures despite being screwed over by the government a lot (not to the extent black people were, but still badly) ... and you've basically got the mess that is America in 2025.
There's a mix of justifiably mad people on both sides, outright racists, and people that serve to benefit from the conflict never ending politically.
(Perspective of a white guy originally from Appalachia that has seen a fair bit of the country and world now ... and largely no longer agrees with the Appalachians politically ... but is trying his best to explain a very complicated and touchy subject without writing a novel or making a bunch of people angry ... your collective grace is appreciated)