I think the issue is not so much that what we are eating is difficult to understand - I am sure that most people would get that eating unprocessed natural food is the best thing if they stopped to think about it - but it is a much more complex issue than what we put in our mouths. Emotional eating, peer pressure, the advice of government, addictions, allergies, intolerances, the power of advertising and the media to influence what we eat, even the fact that there is so much information, a lot of contradictory, that even a simple message like eat natural unprocessed food becomes confusing. There are lots of apparently healthy eating diets (used in general sense not in the weight loss sense) that put rules on eating where they just don't need to be any - don't eat fruit, avoid diary, don't eat wheat, don't eat this or that, eat more fat, more protein etc etc. It is hard to tackle a national/global issue like food when what we eat is very individual and personal - it depends on where we live, what we can afford, what is available to us, what our personal tastes and requirements are and all that sort of thing and yet governments are supposed to issue message where one size fits all. It is fraught with difficulties and the potential to send confusing and mixed messages.
I don't know. I think that we should avoid any way of eating that has a name and I include things like Paleo in that too. It is too prescriptive and, from what I was reading earlier this week, even Paleo isn't that isn't necessarily great either - too high in protein and low in fats.
I haven't read the book in question (I am just about to download it though!) but it seem more and more obvious to me, as I struggle with my weight, that we should eat as I did as a child (I am old) - the meat and two veg thing. We had pudding but usually diary and fruit based and a bit of homemade pie thrown in. We had a sandwiches for lunch and cereal for breakfast but snacks and treats were reserved for the weekends/special occasions or we had a bit of fruit (half an apple or a satsuma before bed). We weren't deprived by any means or hungry for that matter. It was a bit boring mind you but that was more to do with the tastes of my parents than the concept. I am sure I could make it more interesting with the food that is available these days (and of course that is another issue - the sheer volume and variety of food that is available to us).
And of course it doesn't matter what you eat, if you eat too much of it you will put on weight so more realistic ideas of what an appropriate portion size is would be helpful. I don't think we understand what that is any more.