I'm one of those who don't like cruises. And by the way, I went on an Alaska cruise and everyone was not old, nor were they in bed by 8:00 everynight. The things you see on an Alaskan cruise are simply amazing. I loved what I saw, I did not love being on the ship.
I feel constrained on a cruise. And I get bored - I don't like cheesy shows and games. I'm embarrassed for the performers - yeah, I know, I'm wierd. I don't like the casino. I don't like to sit around and drink/talk. I don't like to sun bathe or swim in the pool.
Even with all that, I do think everyone should take a cruise, at least once. The first time I went, it was sorta novel, but I was bored with it after the first 3 days, so day 4-7 were not too fun. Also, I didn't like worrying about getting back to the ship on time, during port times. I felt I was always watching the clock to be sure I got back before the ship left
I know many many people who love cruises, and I know that I am in the minority - but I think you should hear from someone who doesn't particularly like them.