One response to the failure of the Lucas project was the rise of New Keynesian economics. This basically went back to ad hoc assumptions about wages and prices, with a bit of hand-waving about menu costs and bounded rationality.

The difference from old Keynesian economics was the effort to use as much maximizing logic as possible to interpret spending decisions. I find NK economics useful, if only as a way to check my logic, although it’s not really clear if it’s any better than old-fashioned Keynesianism.