I agree that Grand Cayman no longer holds any appeal to us. We have been there seven or eight times. We will be there next week on the Carnival Glory and have already decided that we'll just stay on board.
The one thing about Grand Cayman that is different than other Caribbean ports is that Grand Cayman doesn't "need" cruise ship money. It is far from a "poor" country that relies on tourism. The average income is over $57,000 USD/year. The 279 banks on the island bring in a lot more income than Carnival or all of the cruise lines.
The cruise lines aren't going to "force" them into anything.