The Democratic Party that gave you FDR's New Deal, or Bill Clinton's economy, or hell even Barack Obama, is just gone. You have some well-meaning but misguided people here and there but on the whole, the dems are just the left-flank of the right-wing party that's moved very far right.
The DNC didn't even endorse Zohran Mamdani, even after he tried to water down some of his more radical policies and reassure the rich people of NYC wouldn't be affected too much. That should be enough to to tell you this is not a party that tolerates genuine left-wing politics.
It's not that I particularly enjoy pointing this out, either, it genuinely kinda sucks that America has two parties that fundamentally are really not that different aside from how they treat a handful of social policies, and even then, the Dems seem to be abandoning the cause of transgender rights.
It's just one big party, with two major factions that slapfight eachother but ultimately work together to fuck over as many people in as many countries as possible on behalf of corporations and the military industrial complex. Not very "democratic", if you ask me.