I agree with you for the most part, but like most foods, there are exceptions. Even in simple recipes. We got our last church fish fry of the season last night and whomever makes the mac & cheese sides there knows what they're doing. They use cavatappi w/o ridges and a sauce that's more bechamel than the usual yellow cheese glop. I'm not sure if it's more than one cheese, certainly a milder white cheddar, but I think there's something else in there like muenster or jack. Fine by itself, or I'll amp it up with some piri-piri.
As far as putting mac & cheese on a pizza... I am generally against putting carbs on top of carbs or inside other carbs. And especially putting carbs inside carbs on top of other carbs (as in a Pittsburgh pierogi pizza).