I wouldn't agree with everything you say, but I would add that we probably don't understand everything about nutrition and deviating from millennia of traditional dietary intake including is possibly a dangerous thing to do.

That being said, it can hardly be stated that the modern diet is at all reflective of what humans have eaten in anything but the very recent past. Processed foods and carbohydrates, grains, meat from animals that have been given steroids and have not been free to roam. There are so many variables that it seems like a very difficult task to determine what comprises a good diet.

It is not clear to me whether a carnivorous or a vegan diet would be more beneficial to one's health.