We're in agreement. The mainstream left abandoned their economic agenda because their economic agenda was stupid and as the 20th century progressed that became

We're in agreement. The mainstream left abandoned their economic agenda because their economic agenda was stupid and as the 20th century progressed that became ever clearer, until the steady collapse of the USSR in the 1980s finally made even the dimmest of voters lose their appetite for it. So by 1990 the left lost interest in economics, and began the pivot to race/gender/sexual intersectionalism. They even explicitly rebranded themselves. Clinton's Third Way campaign was adopted with vigor by Tony Blair, who even renamed his party New Labour to emphasize the break with the past. And Third Way/New Labour leftism was not particularly committed to intersectionalism at that time, even though such tendencies did exist on the left since the 1950s. In fact intersectionalism was rejected by mainstream left wing parties - look at the treatment of Sister Souljah then vs what would happen now - but it kept ramping up and by 2012 that had turned into full blown culture war. The new left went all-in on things like "defund the police" that would have been mystifying to a typical 1950s leftist. None of this means the left moved right, unless you only care about economics in which case it's true. They simply dropped one set of causes and picked up another, with exactly the same kinds of tactics and aggression that characterized their campaigns 100 years ago.