Since there are environmental impacts of land use, it seems we should maximize the return from each unit of land, to minimize the impact per unit of benefit.

Now, compare the value returned by an acre growing feed grain, to an acre collecting solar energy via PV. The latter has enormously higher return.

The argument you are making is not an argument against freestanding PV, it's an argument against agriculture. And yet, it is selectively applied to PV.