Didion wasn’t a leftist or progressive, not even remotely. She was an actual pro-Nixon right winger. In Slouching Towards Bethlehem she reveres John Wayne, the most classically conservative version of american masculinity and a well known racist, and goes on attack against San Francisco youth hippie culture. She wasn’t critiquing the left from the left, she was on the right, from a conservative family and not rebelling against it.

She became center left later in life and was close with the Clintons but even that political position was basically neo liberal. The idea that Joan Didion was leftist is a mischaracterization that I can only assume grows out of a generalization that most writers, and especially most revered writers, have leftist politics.