New York really fell off because they capitulated to the "gangster" trend started by NWA. Before NWA, there was variety - you had BDK, Rakim, Kid N Play, Chub Rock, De La, EPMD and on and on and on. All with different flavors, etc. After NWA, when all the record labels only wanted to sign some form of crime rhyme, the originators of hip hop were at a crossroads. Unfortunately, it chose to go gangsta and so afterwards came Wu, Nas Escobar, Lox, ONYX,Mobb Deep, Jay-Z, DMX and on and on all having a theme of crime related rap. Gone was the variety. And some people at the time tried to push back - De La, OC, Jeru, Grim Reap from Gravediggaz. But the machine was too strong and hip hop descended into the criminal cesspool in the mainstream that's lasted 30 years now and seen the rise of trap, drill and other detriments to the music/community.
And I liked a bunch of those acts because they were TALENTED no matter what the subject matter was. That was never a question. but once criminal related rap became ALL YOU HEARD mainstream wise, a dark cloud fell over the music that's never lifted.