Desalinization is an extremely energy intensive process for the amount of water we use. Eventually we probably will produce so much energy that that’s less of a concern, but at the moment we’re having plenty of issues getting our fossil fuel usages lowered without adding Desalinization to our civilization’s requirements.

Desalination can be achieved using the cheapest energy source there is, solar.

Desalination requires high energy inputs. It also creates highly salted water as waste (some gets cleaned, other water gets i cleaned) that is difficult to deal with. Given cheap energy and somewhere to store the waste water, it could be viable.