At the top of my list, is Chefs de France, I'm not sure if Disney / Epcot has told the staff their to be incredibly rude because it's "French" etc., but my last time there my waitress threw a fit when we asked to split our bill, and literally grabbed the receipt out my hand and stormed off. I will never, ever, go back there needless to say.....
The other thing I've noticed, and hopefully this has changed because of COVID etc, is that Disney restaurants were desperately trying to get you out of the restaurant, rushing the food, rushing the drink, rushing the bill, trying to jam as many people through the doors as possible. I noticed this a few years back at Le Cellier, in and out in 30 minutes seems to be the goal. If I'm spending "alot" of money on food at Disney / Epcot, I really want to be able to relax and enjoy it, not be rushed, "are you done," "do you need the bill." etc. Like I said hopefully this has changed.
As a side note, I will say almost 95% of my experiences have been awesome, but they few bad ones stick in my head, with regards to restaurants.