I don’t know if it’s really taken that long. A lot of politically active Americans have been saying this for going on 40 years now.
The crushing defeat of Mondale in 84 led the party to abandon anything even remotely working class, then Clinton’s “triangulation strategy” in the 90s cemented the Dems as a center / center-right party.
I remember reading articles in 2004 about how the Overton window had shifted so much that Dems were right wing.