This whole line of argument presupposes that there is some sort of magic ratio of nutrients for each person and that if they don't hit exactly those numbers they will suffer some vague disastrous consequences (coughing a lot from eating too much pizza and mac-and-cheese?).

Our metabolisms are way more adaptable than that. Generally if you're even in the right ballpark you are fine. There's clearly no exact optimal diet (even at an individualized level). If it were this way people would be keeling over left and right.