When we went to Alaska, we did not go on
DCL, and we booked most of our excursions independently (which I would recommend).
Some excursions will be time of year dependent like bear watching or salmon runs. Others, like whale watching, are not. Helicopter trips with glacier landings have a high probability of cancellations, so always have a back up plan.
To be honest, Alaska is so awesome I cannot see how you could not enjoy it, but I will say that you should get out of the town in Skagway as it’s a very small town and usually has three ships a day which takes away from the authentic feel. This is one consistent complaint I read over and over again from people who did not realize this beforehand. Some let it ruin their experience.

We did salmon fishing in Ketchikan with Nick at Chasin’ Tail Charters (an amazing guide who put us on fish at a time of year when others swear “no one catches fish...too early.”) And we had an amazing time with the eagles!
We went with Beyond Skagway Tours in Skagway who took us into the Yukon on a private tour specifically designed to our interests.
Juneau was our one ship-based excursion which was an underground gold mine which was very interesting. We did this mainly because my mom wanted to gold pan and we needed an accessible excursion. Our guide, John, was a Native Alaskan and a font of knowledge.
The best thing about booking independently is smaller group sizes and being able to really talk to locals and get a feels for what life is like year-round and e actually what kind of people live in the great land.
Enjoy your trip! I cannot say enough how AMAZING Alaska is.