A cruise ship always strikes me as being a slightly more upscale caravan holiday. You're stuck in a metal box with either a lot of old middle class people or a load of drunk lower class yobs. Only unlike a caravan you're stuck on it.
My worst ever holiday memories are being stuck in a caravan in the late 1980s in wet Wales with way too little room and way too many loud drunk people who kept going until 4am every single night.
Cruise ships are like that only you're completely at the whim of the cruise line. You have 0 freedom and you have to deal with all the tax-evading fake-flag BS which seems to rule the sea.