When asked for advice you'll get the best recommendation scientists have at the time it's given.
No, you won't — at least not from the FDA or USDA. That's because the "food pyramid" was designed on a specious basis, the idea that eating fat makes you fat. But humans have known for centuries that eating carbs make you fat. And on the basis of one NIH study which showed that taking drugs to reduce your cholesterol levels also reduced your risk of heart disease, we were told that eating cholesterol raised cholesterol levels though there was no evidence for that, and that eating carbs was the way forward though there was no evidence for that.
So no, your central point is nonsense. Scientists actually knew that the ideas put forth were bullshit. Now, doctors didn't know. That's because they're not half as clever as people think they are, but they like to sound clever, so they simply repeated what the government told them.