I think what it really highlights is that, for most food items, there is no right or wrong answer as to how good/bad it is for you. There is some directional information, but even that should be taken with limited confidence.
Exactly - there are correlations, but there's no definitive answer either way. For some people, a high-carb diet may lead to weight gain and increased levels of LDL in the blood -- while others on the exact same diet may not see those issues, even with the same diet. We don't know what causes the difference, and it may not be possible to design an ethical study to discover it.
I think what it really highlights is that, for most food items, there is no right or wrong answer as to how good/bad it is for you. There is some directional information, but even that should be taken with limited confidence.