Carnival's late arrival to the repeat passenger game has always baffled me. Look at how so many (including me) are striving to get points on RCI, which means more cruises being sold. I can board a Celebrity ship and get the same status as I get on RCI, even though we've only done 3 cruises on Celebrity. Same for Celebrity fans who decide to try RCI. Sonny would get a five-star generals cruise card on Celebrity just on the basis of his 40+ RCI cruises.
I do like the amenity of free laundry on Carnival for the current 10-cruise repeater level. That is really nice.
But absolutely, a higher lever equal to diamond plus on RCI would be a great idea for Carnival.
Sure, all the repeater clubs and societies are at their roots sales tools, but they work and have appeal.