So, here’s the history of macro in brief.
1. In the beginning was Keynesian economics, which was ad hoc in the sense that on some important issues it relied on observed stylized facts rather than trying to deduce everything from first principles. Notably, it just assumed that nominal wages are sticky, because they evidently are.
2. In the 1960s a number of economists started trying to provide “microfoundations”, deriving wage and price stickiness from some kind of maximizing behavior. This early work had a big payoff: the Friedman/Phelps prediction that sustained inflation would get “built in”, and that the historical tradeoff between inflation and unemployment would vanish.
7. The Lesser Depression arrives. It’s clearly not a technological shock; clearly, also, nobody is confused about whether we’re in a slump, as the old Lucas model required.
In fact, it looks a lot like what Keynes described, and old-Keynesian models work very well, thank you, both at explaining it and in making predictions about such things as interest rates and the effects of fiscal austerity. But the descendants of the Lucas project know that Keynes was wrong — it’s what their teachers and their teachers’ teachers have been saying all these years. They cannot accept anything resembling a Keynesian explanation without devaluing everything they’ve done with their intellectual lives.