I’ve had physicists say similar things to me, an engineer, about the courses they teach or have taken. There’s the very basic classes taken and as their education progresses people become more specialized in an area or department. The entire medical field is broken up into many specializations, I don’t see an issue with one more such “department” that deals with nutrition. Overseeing those dietitians or nutritionists could be another story, unfortunately, although levels of quality exist for any type of worker.
I don’t think the responsibility of knowing what a quality diet is falls squarely on the medical field. The CDC has information online for anyone to view, if they have access. K-12 education systems, and the worldwide equivalents, could also take on some of the responsibility.