I was traveling with my parents and while this was not their first cruise experience, it was mine and I didn't know what to expect other than it would probably be boring since HAL caters to an older demographic (i.e. 50+). My sister and I are both in our 20s and most of the activities & entertainment were kind of meh --- nothing really appealed to us (except for the cooking class which my sister loved). They had a bunch of activities like trivia, bingo, auction, and some fitness activities too but generally nothing upbeat or exciting for the younger 20-30s year old crowd.
Actually, the slow pace of life on the cruise was exactly what we were looking for. We did not find the cruise to be boring at all. In fact, it was a rather relaxing vacation for us since we are so used to land tours and trying to do and see a million and one things on our tours. On the cruise, we just lounged around all day when we were at sea (which was only 2 nights) and had plenty to do and see when we were at port. Alaska is really beautiful, especially Glacier Bay, so spending time just admiring the scenery isn't bad.
We booked the land-facing Deluxe Verdandah Oceanview stateroom, which had its own balcony and spent most of the day enjoying the scenery and trying to spot wildlife --- we saw dolphins, seals, otters, and a humpback whale. Pretty relaxing.