Here's how I see it:

1960's-70's - US oppositional politics were based on two points: opposition to the Vietnam war and class/ economic analysis. Other issues were widely framed as secondary. Earlier victories in the civil rights movements gave whites the idea that black oppression had mostly been addressed. Gender issues were sidelined. LGBT and native concerns were so marginal they didn't even register.

1980's-90's - The Reagan years and fall of the USSR created the neoliberal "consensus". As Thatcher put it, "there is no alternative". Electoral politics gave up on economic issues. Unions lost practically all power. Liberals, who already had very little ideological direction in the first place, were rudderless.

now - Millennial liberals and activists have flipped the script from their Baby Boomer predecessors. "Identity politics" are front and center while class analysis has been abandoned. Politicians and bureaucrats from marginalized backgrounds have greater access to the levers of power by side-lining the working class. Liberals even soft balled the handling of 2008 crash.

The liberal-left ceded the working class to the right. Even 90's rallying point of anti-globalization has become a key plank in the right-wing platform in both the US and Europe. Not sure how to explain the piss-poor anti-war movement of the 00's, though Obama and Clinton taking the reigns from Bush Jr. put the final nail in the coffin.