With Holland America, and probably most cruise lines, itinerary and length of cruise make a big difference in the passenger demographics.
We sailed 21 days on a HAL Statendam Asian Cruise. The passengers on this cruise were definitely in the "older" and more sedate category. The ship was deserted after 10 p.m. and during the sea days the lounges had many people sleeping in the chairs. There is nothing wrong with that. It is just an observation.
On the other end of the spectrum, we did a seven day Caribbean cruise, on the Amsterdam, it was a very young crowd and what I would call a bit "rowdy". At night the casino and lounges were very busy.
I guess it all depends.