I struggled for while as well on whether to keep going to Hawaii or try somewhere different. We had been going to Hawaii for decades, but one year my wife had a trip to New York, so I tried Cozumel. It was a bit more money for the flight, plus one stop in Houston, but did arrive at noon in Coz (United now) and was in the water by 2pm.
Now I am "hooked" on Coz.
Why, well from the airport to the hotel is just a matter of minutes using shuttle (average price about $8).
Restaurants are plentiful and the food is good. Lots of selections, from Italian, Cuban, Argentine, etc. Prices are much less the US.
Service at resorts, restaurants, dive shops is wonderful. People in general are pretty darn friendly in COZ.
Booze. I like to have my beer and Margaritas. Beer is cheap, fairly decent selections of brews and the Margaritas, well hey it's Mexico.
Resorts/hotel range from budget to quite fancy, but in my price range 80-100 night you can get a really nice setup with an outrageous ocean view, something that is impossible in Hawaii unless you quadruple the price.
Diving. Well I had always gone to Hawaii mostly for the surfing and really only did snorkeling there when the surf was down.
That being said I feel the diving in COZ is great and again it is much cheaper than it would be in Hawaii.
If you do a bit of a search you will find many good dive ops, and resorts here on SB.
Good luck and if you do decide on COZ you will not be disappointed.