There'll be no engine room tours, either - this is for safety reasons.
The best thing about cruises is that you can do what you want, not what other people expect of you or what other people would do if they were in your shoes. If you want to just "cruise" through your sea day doing nothing, that's perfectly fine.
I'm very active on cruises. I will spend a lot of time in the gym, and get stuck into activities like trivia and silly pool games etc. It's very sociable if you do participate - I think that I get out of a cruise in proportion to what I put in. But that's not everyone's cup of tea, and a two night cruise is not long enough to get to know anyone well.
If, however, you do want to go the active, sociable route, one hint: Identify the cruise staff and use them as your framework. This is the department that is headed by the cruise director and is basically the front line of the entertainments/activities department on board. The cruise staff will be the people running the activities, meeting/greeting at receptions and cocktail parties and at the shows etc. They have to be outgoing people to do that job; they usually love it when pax go and talk to them, as most pax are actually too reserved, shy or snobby to do so. They also know where everything happens, and when.