OK... I similarly never understood cruising, as I (thought that I) inherited my mother's terrible seasickness and I just don't like the water (classic Scorpio, never learned to swim, don't see the appeal to sitting on the beach). My wife (typical Cancer, the water is her happy place) LOVES cruising. Over the years I've grown to enjoy it. My experience so far has been limited to Celebrity (yes I've been on the Solstice above) and Royal Caribbean.
As one tour guide put it, it's a vacation sampler platter. Not sure where to go? A cruise ship takes you to several different ports so you can get a taste of each. Our next trip leaves from Miami, then stops in Bermuda (never been there) before crossing the Atlantic (another first) to stop in Cork (Ireland), Portland (Dorset UK), and Le Havre (France), before landing in Southampton. One big thing that a lot of people miss (even experienced cruisers) is that the point of cruising is not being on the boat. The whole point is to get off at each port and do something.
From the outside they look like the biggest, ugliest sardine cans you could ever imagine. Inside, at least on the lines we've been, there's plenty of room to stretch out. If you want to be in the crowd, you can go join the crowd. If you want peace and quiet, there are literally hundreds of small alcoves and hidey-holes you can go and sit and read quietly. Or you can do any of the dozens of activities available each day. And no, it's not the scavenger hunt silliness that they showed on The Love Boat. I've been to fascinating history and nature lectures, I've watched artists create blown glass sculptures, I've taken an art class, and I've attended more wine tastings than I should admit -- all without leaving the ship.
There's much more to them than buffets and casinos. Yes some people go exclusively for that, but then again some people drive cars simply to get from point A to point B while listening to podcasts! On every ship that I've been on, the casino is just one separate room, smaller than the theater and in a couple of cases, smaller than the pool. The buffet -- again an incidental, not the focus -- is there in case you slept the day away and missed lunch in the dining room. Nobody is expected or even allowed to spend all day there stuffing their face. The food in the main dining room(s) and specialty restaurants is world-class, and the portions are not gluttonously huge. (My fellow Americans tend to complain about how small the portions are, until they get to the third course and they're too full to continue.) The wine, particularly on Celebrity, is insanely good. Solstice-class ships (Solstice, Silhouette, Eclipse I think... ) have a huge brass-and-glass sculpture in the main dining room, 2 stories high, which is the main wine cellar. And that only holds a fraction of the wine varieties actually on board the ship.
Every ship I've been on has had active stabilization. I recall one cruise our departure was delayed several hours while a dive team replaced a damaged stabilizer. I sat out on the deck and watched, it was pretty interesting. Which brings me back to seasickness: Modern ships are incredibly stable (when everything is working properly). There's some rocking which of course is dependent on weather and the ship's speed. I have been on 2 cruises where you really had to concentrate on walking. The first was due to bad weather, the other was when the captain was full-throttle to make up time (I believe it was the stabilizer cruise). I have found that I don't even need seasickness meds on a cruise ship.
Environmentally they have come a very long way. The ships are now designed to minimize disturbance to marine animals. The diesel engines do not run the screws directly, instead they run generators and the screws are spun by electric motors. IIRC something like 90% or 95% of the nonmetallic solid waste collected on board is incinerated to generate power (I think they said that 2/3 of the power above the water line comes from waste). This was all learned on a behind-the-scenes tour, another fascinating way to spend a morning at sea.
You will meet people, but you don't have to spend any time with them if you don't want to. We've made great friends and we've met people who we'd have liked to chuck overboard (on the same cruise, in the same group). We've also gone on week-long cruises without saying two words to anyone but the crew. We've met great people in port towns -- the person who described cruises as a vacation sampler platter was the captain of a sailboat we had chartered in St Thomas. She was retiring and asked us in all seriousness if we would be interested in taking over her business.
I'm not insisting that cruising is or should be everyone's favorite vacation (I still have other things I'd rather do), but if you get a chance to go, try it once or twice. It can be a lot of fun, it can be educational, it can be relaxing... or it can be miserable if you really want it to be.