this is my experience from working in many restaurants (not as a cook) along with being a foodie. While food tastes differ and is subjective, all you'd have to do is compare the best restaurants menu with a food buffet.
There are hundreds if not thousands of amazing dim sum restaurants in Hong Kong and Saigon that prove you wrong.
Beyond that.... as a former back of the house restaurant employee (10+ years, Cordon Bleu, blah blah) I can tell you that the only time fewer dishes is a guarantee of higher quality is when the staff isn't skilled.
You can go through several lists for the top 50? restaurants in the world will prove you wrong. Not one is chinese and I doubt any serve the traditional dim sum style with the carts rolling around.
