Great question. . .I am admittedly overly critical of Disney Dining because I have been eating there for over 20 years (from a qualified standpoint) and find over those 20 years the quality overall has become mediocre at best while the prices even at the best possible restaurants are insulting.
If one has a car and doesn't mind leaving the Disney Magic, or if you simply walk to Dolphin or Swan, you'll find what Disney dining should be.
Anyway here are my top 5 never visit again (assuming management doesn't change) and (there are way more than five):
Kona Breakfast was awful. Fat, sugar and some corn syrup added on top of fat and sugar to hide how horrible the food is. Crap Kona coffee knockoff. Service was atrocious. Shameful.
Yachtsman. . . overrated. Meh service as well. Shulas would put them out of business if Disney didn't protect them with the
DDP (Frame of Reference: Chicago steakhouses - if you're going to drop $60 to $100 a person, you should be at least as good as Chicago Chop).
Le Cellier. Apparently Salt is the chief export of Canada. The move to 2TS credits was ridiculously arrogant. Service is good though, but I still won't go back.
Chefs de France. Do I even need to elaborate?
Every TS restaurant at MK. . . why do I have to leave the park to get a decent TS meal? (pre-Fantasy land expansion since I haven't been since.)
I do have favorites too, and there are some gems, but that wasn't your question.