I agree with ESS that the entertainment is an "extra" and consider it part of the whole cruise experience.
I went on my first cruise May 29th on the Sapphire and I appreciated that there were so many different types of entertainment for me to choose from.
I went to the production of "Piano Man" and found myself singing all of the songs and smiling to myself at the different memories that they brought back. I really enjoyed the playing and the sound of the "piano man" - I believe his name was Francois - during this and other performances on the ship, yet most passengers were impressed by the singers and the costume changes and not by the music. Go figure...considering the name of the show...
I also caught some of the Andrew Lloyd Weber tribute on the ship but it really wasn't for me. I think I may be the only person who has never seen "Cats" or any other ALW production. Yet there are people that would love to see a production like that on a cruise ship.
I found myself laughing at the bad jokes and being impressed by the amateur magic tricks.
From what I heard passing the theater, "Curtain's Up" wasn't my cup of tea yet the Tea for Four Quartet was. To each his own.
I have to admire the performers even if they may not be the quality musicians and singers that some passengers expect to see. I can't do what they do ON LAND, let alone AT SEA! No matter how much I enjoy singing, I don't think the school of "if you can't sing good, sing LOUD" would get me past the audition.
The entertainment for me didn't make or break my cruise experience, and it won't be a deciding factor for my next cruise...although...the Dave Koz and Friends At Sea cruise does sound reaaalllly tempting....