He strikes me as one because he told Carl to take the safe route making a normal sandwich instead of letting Carl be creative with the sandwiches he wanted to make, Riva also strikes me as someone who would rather be in control of his employees instead of giving the customers a highly satisfactory experience at the restaurant.
shareRiva was a businessman, not a chef or an artist, and it showed. I'd argue that he wasn't a very good businessman, either, since anybody in the food industry at that five-star level should know that part of the appeal of a master chef in the kitchen is that the master chef creates new dishes and changes the menu. One food industry professional told me that if a restaurant doesn't change its menu at all within three years, it's not really a top-quality restaurant. (This person was specifically talking about five-star restaurants, not something like a steakhouse or a family restaurant).
Riva should have either trusted that his chef was the master of the kitchen and let him play, or fired him and hired a better chef. Now, the movie does give us a small out for Riva where Carl tried sweetbreads that just didn't sell, so I will give Riva a small concession there. He was likely a little nervous about letting Carl branch out after that. He also had a point about the Rolling Stones playing the hits.
Ultimately, though, he should have seen that Carl was excited about trying new dishes and known that that would translate into great food, especially with the other cooks in the kitchen raving about it all earlier. Could he not have instructed Carl to offer some choices? Let the regular customers hear Jagger play Satisfaction and give the food critic a sampler plate of the tried-and-true plus the new menu?