almost any "traditional" food seems to taste better than almost any "modern" food.

First, it is bad form to generate a new theory on the basis of your own personal taste. Second, where are you getting your information about what "traditional" food tasted like? Is it from nice restaurants that serve traditional food? Do you think such menus are reflective of what the average person ate 150 years ago? Big Macs are way better tasting than bread crust and mash.