> Is there really any doubt that if we cover massive swaths of land in solar panels the soil will become useless?

To me it is obvious that the soil under solar panels will be extremely healthy and useful, which is evidenced by the abundance of growth underneath all the solar farms in Minnesota fields. But perhaps you think the answer is the other way? Where have you seen only mud under solar panels? How did they build them such that nothing grows? And mud is far far better than current monocrop farming.