We had a nice quiet lunch at Tutto Italia in the Italy pavilion in EPCOT recently. I was shocked how empty the place was. If you sit in the little alcove area off the main dining room you get a nice view of the lagoon and of the whole pavilion square. It was a very pleasant surprise for us.
You mentioned having eaten at Sanaa, otherwise that would be a big recommendation of mine as well. A window table overlooking the Savannah is such a great experience, and their lunch menu is my favorite.
The Hollywood Brown Derby at Hollywood Studios could be a good option if you eat at an off time. Otherwise it gets crowded quick. Excellent food though, so we always eat there regardless!
At the resorts, perhaps the Wave at the Contemporary or the Grand Floridian Cafe, as others have noted. Both are less likely to be busy and offer great food. Personally, my husband and I made a lunch trip to Kona Cafe a few weeks ago on our last day and we were extremely unimpressed, so I can't recommend it. The food was just OK and the ambiance at the Polynesian Village in general is really loud, hectic, and unpleasant. Unless you sit way back in the very back of the restaurant you are literally on display to the lobby, as well. It's weird having an audience while you eat.