I have cruised on all 6 mass market lines. I'm only interested in ocean cruises. Before I tried cruises, I used to do land vacations. Would never do those again. I found my niche: ocean cruises. I don't have to think of where I am going to eat breakfast, then lunch and then dinner. I just have to show up at a restaurant. Someone mentioned lines? I don't stand in lines because there are many restaurant options. With cruises you unpack once. Only about 10% of the US travelers go on cruises. I just love being on deck and turning 360 and there's nothing but water. My best day on a cruise is a sea day. It's not for everybody. Just choose what interest you!
Some people like to highlight the crowds on the Lido Pool deck. But there are many quieter places to read, nap, play bridge, do crossword/sudoku, spa treatments, etc.