The beauty of a cruise is that there is so much to do that appeals to all ages and tastes. You may not enjoy some of the entertainment on the ship, but others will disagree. I would like to see some other types of entertainment as well, but I am confident that the cruiselines have taken much time and energy to determine what the most amount of cruisers would enjoy.
As for adult comedy acts, they do have those late at night, and they specifically specify that it is of an adult nature before they start there schtick. So, if anyone gets caught in one, it is there own fault.
As for paying for entertainment, I cannot disagree more. I love cruising because it is an "all in one" package. All I need to bring is some extra cash for drinks and entertainment off the ship, and maybe a night of blackjack.
I think your are making some assumptions for other cruisers that may not ring true. My advice to you is to do the things that interest you and don't do the things that don't interest you. I guarantee you will have a blast and not be bored at all.