Tough question - "How to please all the people all of the time!"
Answer: You can't ... but you should be able to achieve a level of consistant quality!
Carnival's Triumph did a terrific job by bringing the Mexican Folkloric Dancers aboard, in Cozumel, for a 90 minute show in the main room that was wonderful. The rest of the cruise we sought the smaller clubs for jazz, piano and dancing - though the latter was difficult because the music was directed toward the under 30 groups.
One piano player, a duo or trio - to us is more intimate and enjoyable because you make a connection if the music/talent is genuine. I enjoy good live entertainment but become uncomfortable when it is obvious the performer is out of their element or expected to deliver beyond their capability.
I'd enjoy a good presentation by someone knowledgable in a particular topic, monologues or readings like, "An evening with Mark Twain." A good 3 act play or some adaptation of a classic role could hold possibility. What about summer stock theatre type reviews that might even have a few "names?"
Whatever direction the industry takes - they'll have their detractors. My sincere hope is that crude humor is never offered as "the acceptable norm" in the absence of an alternative for real talent and the cruise lines raise, rather than lower, the quality bar.