Truly KD the whole issue is skewed by the recent abominations that have happened to the food supply when it comes down to making practical decisions on what is healthiest to feed oneself or ones family. You make some excellent points.
Here's a perspective. When I very first learned that food could change one's life it was because I was put on a cleansing diet. There was a long list of things I shouldn't eat for three weeks. I had to try to figure how on earth to do it and for the first time walked into one of the rare health food stores at that time. It changed my life.
Now, that gave me the perspective that cutting things OUT of ones diet could be magical. I didn't go on a diet to lose weight, or choose a particular diet that I thought INCLUDED anything particularly healthful.
I had a hard time continuing with cutting out almost everything, so as I moved forward I continued to cut out things - but what I thought might be the worst things first. For instance, cutting out soda/pop improved how I felt. But when I cut out all sugar and fake foods like twinkies and Spam it made a DRAMATIC difference for me. One by one I tried cutting out things that weren't natural or what many said were not healthy foods and adding something that was natural and felt better and better until there was a baseline at which I was simply really darn healthy and happy pretty much all the time. It wasn't until I tried eating raw foods that I realized that I never really understood what the word "healthy" meant.
The furthest that I ever got to looking backward before relatively recently to what people would have eaten a long time ago and what a really natural diet was to thinking that we didn't always have fire and no other animal cooks their food. I just got on the internet in the last couple of years btw. Until then - I had only read a couple books 30 years earlier.
So today, with all these different gurus and diet plans and philosophies and inquiries into what the "true" diet of humans is what I have noticed is that different people feel good or great eating a very wide variety of regimes and some make regimes into religions and then there's no telling if they actually feel better or just are fundamentalists who are too unwilling to admit to anything that doesn't fit. That has to be watched out for fer sure when trying to sift through ideas and data.
Sometimes I can't help to wonder if which diet someone ends up feeling the best from is the one that cuts out the most of what is really BAD for that person and fits with how they live - or that they just don't realize that there might be 5 other diets that also cut out what was making them feel so bad....... or maybe they just were lucky enough to find the right one - but that just because it was just right for them means that it's going to be just right for everyone.
I have thought many times that allergies and food sensitivities or inability to digest a particular food are the primary factor in having someone stop at a diet and say THIS is the best one for everyone.
When I met Ann Wigmore decades ago and she had just started putting everyone on this mush of a soup I couldn't help but to think - well - that's because she had part of her intestines cut out from cancer a long time ago - everyone else calls it "cement soup". Because it worked for her (oh - and it sure did!) then that's what she fed everyone no matter how consistently they got sick from it at her center or how much they complained. She abandoned her earlier stance of eating whole raw foods because it was no longer the best diet for HER.
So much of what is available as food today is simply not food. It's amazing that humans can survive on them at all. How can any one of us really say what is ideal for us living in this modern world when there are so few choices of real foods left and finding real food is so darn hard! What was ideal before - even for millions of years - might not be ideal now living in the world the way it is today or in cities or when typing in front of a machine pouring EMFs at me.
I think this way of approaching diet by going back and getting a baseline by seeing what has worked well for eons is a great idea - as long as it doesn't become another box to lock oneself into and as long as we remember that we AREN'T living in that way any more. Our planet is not the same planet, our societies and lives are not what they were, we don't do the same things and maybe even our brains are different and even we as individuals are now so different because we no longer live all pretty much the same way out in the wild. Different people have radically different exposures to toxins, different allergies, different diseases and histories even living right next to one another let alone around the globe. Never before were we raised so far away from nature or exposed to so many truly new substances. Now we have to figure out what's worse at this board meeting - to chew only on this irradiated celery or eat this cooked hormone-pumped burger - and how on earth to find a burger or celery worth eating at all generally! I am the LAST person that will ever say THE perfect diet for all humans is such and such and I highly doubt that even God could do it these day.