That's for basic med school education. Happily, medical education doesn't stop at the end of med school. It is more like, beginning just at that moment. Otherwise many more patients would die.
So yes, on paper you're right. In practice, there are even clinical nutrition specialists and those are MDs.
In practice, nutritional interventions are much less favored over drug interventions.
For example, a simple ketogenic diet intervention can be a very effective treatment for type 2 diabetes. But most doctors still favor the 1960s-era, discredited science saying dietary fat causes heart disease.
So diabetics are given metformin and whatever fancy new insulin came out recently. And then in 20 years, those people will likely lose their feet and eyes.
Well, what can I say. No?