I would also quibble with Paul about river cruises being the same as bus tours. There are similarities, but they are not the same, particularly how the group interacts and how well you get to know the other people (or how easy it is to avoid getting to know the other people, as the case may be). As well as how well you get to know the guides.
It is true that river cruises and ocean cruises are different - and people should understand the difference. I personally prefer river cruises because they address all of the things that I dislike about ocean cruises:
1. I don't like wasted at sea or private island days (I travel to experience the world, I can hang out by a pool and drink at home). There generally aren't full days on river cruises with out a stop.
2. I don't like not being able to see land. (This is a personal thing, caused be watching the Poseidon Adventure as a child, but it is real.) You can always see land on a river cruise.
3. You don't have to take a helicopter to real medical care from a river boat. (I have a daughter with some health issues, and a cousin who likely would have died had she come down with meningitis two days later when they would have been on their cruise.)
4. You can't get lost on a river cruise boat. (Yes, I'm sure that alcohol had something to do with getting lost on our ocean cruise, but still.)
5. A river cruise isn't mass tourism. A river cruise drops off like 150ish people into a location, not thousands.
6. You can walk off a river cruise, no shuttles or jetties required, and often (but not always) right into town.
Similarly, my family doesn't really need night time entertainment, at least not every night. They are all introverts, so a long day of exploring the world requires some time to recoup, in their room on their phones or watching movies. And I usually have to work some every day, so I work most nights. Again, a personal thing, but this works for our family.
And my family aren't foodies. We like good food, and thought that the river cruise food was fine. (and much more casual, which was also a plus for the family).
But a lot of people love ocean cruises - so you do you.