https://blogs.scientificamerican.com/observations/vanishing-...
https://www.politico.com/agenda/story/2017/09/13/food-nutrie...
There is some evidence sugar content has increased, from varietal changes, but that's about it.
But allow me to actually provide some hints that, while not able to remove all doubt about the matter, nevertheless show such a theory is not an undeserving question, nor born from an irrational mind:
https://journals.ashs.org/downloadpdf/journals/hortsci/44/1/...
Specifically what the parent is referencing is the density of nutrients per unit of meat. Are you saying that all meat is uniform in nutrient density?
I'm genuinely flabbergasted by your supremely odd take on this situation.
Nutrition is an area of study which lacks a lot of information. Even as time goes on and agriculture changes, the data we have about the food we consume appears to be out of date. There are many other factors we’re just beginning to become aware of with implications we haven’t begun to unravel.
Nutritional science and the data we have today is completely acceptable to question. Just about everything is, but nutrition seems especially open.