I would hate it I think. On holiday I like to explore at my own pace. I struggle with crowds and noise and timings determined by other people. Holiday is a break from that, usually. I love not having to clock-watch so I can actually relax. I could never decompress in an environment with so many people and so much noise.
I like to see different architecture, historical sites, do road trips to explore remote places, hidden local restaurants. Local food is a huge part of travel for me.
I have been to several remote places by ferry that could only be reached that way, and even then the port areas were the least appealing and interesting. Just the landing point, to then explore the place properly once I'd hired a car and found somewhere less busy to stay.
I want to spend my holidays immersed in the culture and feel of the place I am visiting rather than that be a minor part of it and most of the time be spent with other tourists. Also on these huge ships, most of it is indoor stuff, with only a tiny area being outside proportionate to the number of passengers. The claustrophobia of that I would hate. I like to run on the beach on holiday before breakfast, wherever I am (obviously not for city breaks if no beach but relaxing holidays).
My happy place is on a secluded beach, lazing away the hours with - for once - no pressure to do anything. Tranquility. Feeling the sun on my skin, swimming in the sea. If you end up swimming in the sea on a cruise you are most likely dead. 🤣
People like different things. 🤷🏻♀️ I can see how for extroverted people and people who like organised entertainment etc this would be fun. I like peace and quiet and good local food and wine and relaxation, and being able to be spontaneous about what I do without any time pressure. Also many comments here about how you have to get up early to make the most of it - again, the last thing I'd want to do on holiday!!