Yummitivity = YUMMY!/(fancy decor + celebrity status of chef)
The more money they put into foofoo-ry (ok, I made up this word, it means people who spend more time on superficial stuff than innate beauty), the less resource they have to devote to the taste of the food. Also, if the chef happens to be a celebrity chef, the food is bound to be bad cuz he/she is probably too busy appearing on TV to focus on the food.
Case Point I: Look how beautiful this restaurant is...
Case Point II: Shilin Night Market in Taipei... no foofoo-ry at all!