They have the same nutrients as commercially grown. They have a higher density because theyre smaller and have way lower production. The neutrient declaine is going to happen regardless of you using high or low yield it just a matter of scale and time. All of this started exactly how you believe we should be doing it now. The problem is that doesnt make enough food for everyone and it only takes one bad year and a LOT of people dont get anything. So we selected for traits to stop that. The problem is that now we have to choose more land and resources (fertilizer and energy) to maintain heirloom strains and grow them at scale and transport them around faster and farther than theyre designed to last. Or less quality per yield but far more yield and much longer sheld life. Without forcing everyone to live within a certain radius of an heirloom farm there is only so much you can do before logistics and shelf life simply dont cut it anymore.