After the Camera Leaves the Kitchen-Restaurant: Impossible
For the restaurant owner who go through that, It is an oportunity to change and learn (quick and fast) new things that they could not do otherwise.
New menu items : Some of them will need to be re-tweeked to cater to the real customers; add more sauce, less veggies, less sauce, more veggies ... make the new items daily specials instead of regular menu items, ... have your staff learn new food slowy, introduce those items as you see fit, not how the consultant tell you to do it.
Decor : A bit of quick decor help cannot really make it worse in most instances; again, owners need to use that as a good start to continue remakaing the decor in their own images using what they were "given"
Management : I think this is was is mostly lacking from those awful restautants, they do not look to know how to run a business as difficult as a restaurant; I don't think those restaurant imrovement shows will change much of that!