I have done a couple of cruises [Med & caribbean], albeit on the old Ocean Village ships which were about 1600 passengers and 700 crew, so considerably smaller and very relaxed. You certainly didn't feel like you were confined and living under 'rules'. I would happily do another if I could find one that was as relaxed but adult only too - I should say that for people with kids, they were brilliant, mine were young the first time and we simply never saw them for 2 weeks, so much entertainment. Waking up in a new place every day was great experience both times. The second one, back in 2009, because I knew the layout of the ship, I chose a cabin right at the back, next to a rear sundeck where the adults without kids tended to hang out, a couple of decks above the 24 hour eat all you can restaurant so when we weren't out visiting the latest caribbean island, we could relax and enjoy ourselves, just reading, watching the sunset as the ship sailed out of port, with food close at hand.
In reference to the photo, on both trips, we docked several times with other cruise ships that were absolute mammoths, but I never managed to get a photo that showed the size difference the way that one does.