It seems to me too that the heyday of model years, the 60’s through the 80’s, was all about significant design body changes. That seems to have died down.
Another thing I noted about 1990 was that the “year” seemed to be slipping earlier and earlier until they were unveiling next year’s model in the early summer, and starting to deliver in the middle of the fall. That seems to have died down with the lesser emphasis on new model designs.
I’m surprised nobody’s mentioned Johnny Cash - the ultimate send-up of model year changes.