I regularly (once a year or so) cruise overnight when I take a car ferry from Norway to Denmark. I don't enjoy being on the boat, but we try to eat in a decent sit down restaurant, or don't eat there at all. And we often watch a movie if they have anything interesting. And we shop tax free booze. These ferries have a varying degree of luxury.
My fear against being on a cruise boat for a longer period is that you need to pay for all the food and each drink that you consume. You can't just drink water from the tap like I do at home or like I do at normal camping trips. You can't buy your breakfast and lunch in a normal shop, but have to eat restaurant style. And from the ferry-experience, you can't sit anywhere quietly for yourself, other than in your own cabin. You also need to eat dinner in a restaurant every day. This is something we also have to do if we take a city trip or a week's trip to the south. I do enjoy it, but it is an extra cost that we don't have when camping. I would also be sceptic about not being able to get off the boat. I love to be in a forest or otherwise outside.
I have a couple of elder outdoorsy friends who have gotten into cruising from time to time. They seem to love it. They try to do it in a Mustachian way, by not buying the expensive trips ashore, but finding out for themselves what to do. After they first cruise the male friend went up 8 kilograms (roughly 16 pounds) in weight. That scares me.
I think a ferry experience and a typical ocean cruise are very different.
First, I have never had a problem finding somewhere out of the way to sit where I could read alone in near peace and quiet (maybe in a library where others were also reading, so not alone; or maybe in an abandoned corridor that occasionally someone came down.)
Second- most cruises include food. Perhaps there are pay restaurants where you can get upgraded experiences, but a sit down meal or buffet is always included. (I rarely eat at a buffet on a cruise- with few exceptions, we don't pay extra for food.)
Third- I've always cruised on a ship where fountain water was provided for free (also tea and lemonade). Again, with rare exception, I've never paid for a drink on a ship. (I don't drink alcohol.)
Fourth- the cruises I've had always included room service, though basic, with only a tip needed. If you really didn't want to go to the restaurant for a meal, you could have sandwiches in your room.
We cruise on one of the least expensive lines, Carnival, for the most part (we've also been on Celebrity)- because I don't really want to pay more when it's "good enough". But really, you have to pick the line that is the best match for you.
The lines I am familiar with- Carnival, Royal Carribean, Disney, Celebrity, Princess, HAL, Azmara, NCL all cater mostly to English speaking demographics; but there are certainly lines that don't (MSC does announcements in 3-4 languages?)- none of these are like the ferry experience you describe.