I can’t really argue your point because I don’t know the technical details of wind and solar.
I do know that Qatar built the Ras Abu Fontas A2 unit that is huge. It uses gas to turn sea water to potable water. There are quite a few others in the immediate region. So gas fired technology exists on a large scale.
I’m not familiar with the solar powered reverse osmosis on a grand scale to comment. ...... but I doubt it
I'm not familiar with that either; I was thinking along the lines of a lifeboat survival desaliator writ large. Very simple technology.