Jamaica was never a main stream diving destination, but then it was never ever marketed as such. Diving was like, just another activity, competing with tours, tennis, golf, reggae, .....
The island is large enough and with a large central mountain region offers a variety of enviroments. This topside topography extends into the sea. The south coast tends to be on the flattish side, while the north coast is mostly walls and sea mounts. Especially on the north coast, there is underwater topography that will stand comparison with anywhere. The coral, parcticular near shore - is not immune to the world wide rise in sea temperatures and acidity - is not at its best and largely algae covered.
However, many of the deeper dives (90'+) still has incredible healthy sea fans, sponges, and soft and hard corals. Unfortunately, many of these areas are not resort. Even sites in resort areas may be visited only rarely because dive operators are catering to divers generally not competent enough. Maybe this explains your 'conflicting comments'.