I can see you're getting there, but haven't yet reached the point I have, from personal experience with myself and family members.

There is no one answer to what food/diet is good. Because every human body is an incredibly individual machine. There's no getting around things like some people thriving on high protein diets because their system has trouble with carbs and vice-versa.  And things like that some can eat lots of supposedly "bad things" and thrive (according to the nutrition "science" of the moment,) like those who eat lots of candy and ice cream and don't gain much weight. Everybody, every body, has a different system.

It doesn't even help for individuals to select out for groups, i.e., look how Italians eat olive oil, Asians eat rice instead of wheat. Or to compare the effect of our grandparents' generation wheat to ours. If the science tries to apply what they supposedly learned to everyone, then it doesn't pan out, that's when their case always falls apart.

If you want to put it in an evolutionary context, that's helpful to some, that works for me. Here's how: every individual is at a different point on that timeline. That's why some might thrive with a caveman diet and others would get real sick and die.

Speaking of getting sick and dying, the cavemen probably didn't have our modern moral prediliction for keeping every individual alive, no matter how healthy or unhealthy an organism we were as an infant. They let selection adjust to their diet, not the other way around.

Here's what I have concluded is the true way to an optimal diet for each individual:
an elimination and rotation diet with a diary of reactions and a review with a nutrionist every week
in concert with:
a doctor willing to do similar with regular blood and other testing, willing to go over detailed results with each individual patient, i.e. "now did you feel better or worse when your potassium levels were low?"

Ain't gonna happen in our lifetimes. So you do the best you can if you care. That includes, if you are having health problems, keeping up with all of these cassandras about this food or that food or this food or this diet that diet and looking for clues that pertain to your individual problems. Chances are very high that none of them are saying something that's true for everyone. You take them all with a grain of salt and you look for clues for you alone. Speaking of salt, it's a good example--just because they found a correlation between salt and blood pressure doesn't mean everyone should cut down on it or even that everyone with high blood pressure should cut down on it. Heck, they're not even sure what damage high blood pressure might do to every single human, maybe for some it's there for a good healthy reason.

One good way to keep all the diet stuff in perspective: While most doctors with real experience in this area (and by experience I mean with actual patients and with lots of time with them) will tell you there's nothing better than real food, they can also give examples of people living many years quite well with parenteral nutrition alone, after totally losing the ability to eat. That's because "they" haven't figured out "real food," what it is, and how it works yet. Why does baby Johnny eat mud? Maybe he needs the minerals.