"fruits and vegetables grown decades ago were much richer in vitamins and minerals than the varieties most of us get today. The main culprit in this disturbing nutritional trend is soil depletion"
https://www.scientificamerican.com/article/soil-depletion-aN...
>Davis and his colleagues chalk up this declining nutritional content to the preponderance of agricultural practices designed to improve traits (size, growth rate, pest resistance) other than nutrition.
The part of the article that you've quoted is simply Davis' opinion, not the subject of that study. The author has a different opinion. I don't know who is right, which is why I said it's "not an uncommon view".
I don't know if that debate has been settled. The article doesn't cite any studies examining the cause of this nutrient depletion, and I didn't find any studies of the cause with a few Google Scholar searches for soil depletion and related terms. If you know of any research that answers the question I'd love to read it.
1: https://www.tandfonline.com/doi/abs/10.1080/07315724.2004.10...