OP, I am really sorry this happened to you and everyone else on your cruise. While, yes, Disney did operate within their cruise contract, that does not make this acceptable - especially for a cruise line that markets "magical" experiences and claims to hold itself above and beyond the masses. I am also sorry that some posters seem to think you should have known about the dry dock and construction ahead of time and chosen to avoid it.

The average consumer booking a vacation isn't going to scour through the internet looking for constructions schedules. One thing I have always appreciated on WDW's website is that they make it very clear before you book if there is construction going on at a particular resort.
DCL should do the same.
To me, the worst thing about this whole mess is that Disney chose to wait until after the PIF date to even notify passengers of the construction issue. This was not something that broke unexpectedly and needed to be fixed. While that would be disappointing, it would be understandable. This was a planned event and Disney waited until passengers could not cancel without penalty to notify them. Then, to make things worse they did not clearly state in their email what was going to happen. We hate buffets - all of them, Disney or anywhere. Switching from a sit down, MDR experience to a buffet is a big step down in service in our opinion, and I would be ticked. Closing half of the pool deck food areas for a good portion of the cruise is not OK either. Disney already lags behind the norm in the cruise industry for their number and variety of food offerings on board. To close down a significant portion of them while passengers are on board is not cool.
I agree with most of the posters here, that you should notify Disney of your disappointment. Normally, I kind of roll my eyes at the folks that want some type of compensation when their cruise doesn't measure up to their (often unrealistic) expectations. But that isn't the case here. You simply didn't get the experience that was marketed to you and that you paid a
premium price for. All that being said, I hope that this doesn't turn you off of DCL for good. While it would be understandable if it did, please know that this isn't the norm for how they operate (well, let's hope it's not the "new norm"). We have had fabulous experiences on the five DCL cruises we've taken. While there are always highs and lows and a few glitches here and there, we have never experienced anything at all similar to what you guys did.