There's no doubt that Negril's reefs have been horribly degraded from what they once were. I lived there for a year in the early 70s, and it was a paradise with only one small hotel (Rita Hojan's Sundowner), powder soft coral beaches more than a hundred feet wide in places, stopping at thick jungle. Parrots, Boas, fisherman's shacks on the beach, conch shell piles 8 feet high, and so few tourists the total could be counted on your fingers. No telephones. Starry nights so clear the water and sky were inseparable. No cars. The reefs grew lush almost to the waters edge.
Tourism changed all that and by the late 70s dire warnings were coming from international coral reef preservation groups. By then Negril had become a super hip destination, part of the Hippy Highway and popular with the international jet set. Popularity had begun to destroy old Negril: popularity, greed, and incredible stupidity.
By the 90s Negril was only a dim shadow of its former glory. The construction of a major highway from Mobay to Negril put enough silt in the water to kill all the shallow coral.
The development of hotels on every square inch of the 7 mile beach and the pollution from this mass of humanity and the construction needed to house and entertain them destroyed enough of the barrier reef to wash away the natural sand beaches. If that were not bad enough every hustler, rentadred and fake Rasta in Jamaica was drawn to Negril, which had also become famous by then for its sex tourism aimed at middle-aged American and European women.
I can't go there any more because I remember vividly and painfully what used to be, but I would not write its scuba diving off completely. It's not just a lot of dead brown coral by a long shot. There is still a lot of life on the deeper reefs, and there is enough remaining coral structure around those spur and groove reefs to make diving mildly interesting. Places like the Throne Room and the airplane wrecks come to mind. I would not suggest going there for the diving, but if you are there anyway, I'd certainly recommend a few dives.