In part due to the DLC mostly agreeing with the Conservative position on the economy and to fight back would lose the Democratic leadership all that lovely corporate cash.

Sanders, Ocasio-Cortez, Omar, and some of the other "upstarts" that aren't beholden to Wall Street for their campaign money can and are leading the fight against the Neo-Liberal power structures.  Even so, they are few & far between, and are not supported by the rest of the Progressive (sic) Caucus

She believed in nothing; only her skepticism kept her from being an atheist. -- Jean-Paul Sartre