Personally, I am not a fan of all-inclusives for most areas, but especially for Cozumel. When I visit a place, I like to interact with the people and the culture; to me, an all inclusive is like some sort of diorama that is only barely associated with its surrounding world. I love to go into San Miguel for meals at one of the many fine restuarants. For me, that includes what most people would not call fine dining. For example, I love El Moro, a place that looks like an old diner stuck out in one of the poorest sections of town. But the food is great, and the people are REAL.
A couple of years ago my children (then young adults) were coming back to our hotel in a taxi, and they got into an excited conversation with the taxi driver about the World Cup matches that were going on. They eventually made an arrangement to go to his house and watch a match with him there. They had a great time. That may be more interaction with the local culture than you and your wife are looking for, but I love that sort of thing.
All inclusives do not interact as much with the local economy, either. When you eat all your meals at their official restaurant, where do you think those dollars are going?
To each his own, but I assure you that your wife can have a great time without going all-inclusive. My wife is also a non-diver. She loves Cozumel, and she, too, avoids all-inclusives, for the reasons stated above.