Rorem wouldn’t be the first composer to stop composing, though at 95 it’s more understandable with him. Giacomo Rossini, Jan Sibelius, and Charles Ives, among others, decided in the middle of their lives to give up composing music. Rossini concentrated on cuisine, Ives on his business career, and Sibelius? Well, everyone already knew when he stopped something that he was able to Finnish...
Rossini only stopped composing operas. He continued to compose in other forms. Sibelius was already in his mid 60s when he stopped with about 40 years worth of music behind him. Most great composers don’t even live that long.
McCartney hasn’t written anything worth a shit in 20+ years.