Did an Alaska Cruise in 2005, not Disney (it was Norwegian) but replying as I was 15 at the time and so may still be relevant to the OPs question.
In summary, I hated it as did my mother who was in her 50s at the time. While part of this was having nothing to do on the ship and very low quality shore excursions through NCL (the highlight of one tour being told about a second grocery store in the small town so that if the first sold out, you could go there for milk), the ports were very small and there was next to nothing to do or see in the free time after an excursion. A lot of the excursions being nature themed (and I say that as someone who as a teenager loved animals) got a bit repetitive and boring for a teenager too. It was so bad that it put me of cruising until 2018 when I first tried DCL.
Having said all that, I think DCL is great in terms of always having something to do on board and the port excursions I have booked through them elsewhere have been great, so I am tempted to do a DCL cruise to Alaska at some point to have a better experience.