OK there were many retirees, but not all. In fact AMA does Disney cruises too in Europe.
We've never sailed with Viking, or as AMA calls them, The Evil Empire. Every day we had choices on tours. One of the choices was taking a bicycle for your own tour. If you take a bike, you have to sign the "IF anything happens it's all my fault" waiver. Often there was more than one tour choice, and you are allowed to decide. We never did anything, or went anywhere that we didn't want. There was entertainment in the lounge after dinner. These are not large ships but they do a nice job. We rarely sailed mid-day, so there were an AM & PM tour choices but most of the sailing was early AM, or late at night. We don't do castles because they're mostly just big shells. No furnishings. So there are a lot of options & choices, depending on what you make of it.
The food was great. I'm celiac, and they were very attentive to the gluten free situation, so that was a plus for us.