Actually, while I don't have recordings of the conversations, I spoke to several managers at TS restaurants about the DDP, and they all hated it. All of them told me that they had to buy less expensive cuts of meat/seafood and cut expenses where they could to cover the money they were given. Why do you think that Le Cellier went to a 2 credit restaurant? Because the manager could not give the level of food expected without the additional cost. There is no arguing. The DDP had a direct impact on the restaurants.Unless it can be definitely proven that the dining plan hurts the customers not utilizing it, why not say "to each their own"?
You can't prove the menus were dumbed down (people still disagree on this), prices changed directly due to plan. Maybe you can make a strong case for less availability.
Otherwise, let the people use the plan if they want. We did on two trips(once quick service, once table service) , then didn't on two trips and realized the dining plan doesn't work for us. But if it works for others, I hope they enjoy it.
Now saying that - I couldn't care less if people buy and use the DDP - to each his/her own. I just wish that the top tier menu items, such as filet mignon or lobster were additional cost items so the manager can keep the quality high for those of us that pay cash and still want the filet or lobster at times.