> Plenty of countries completely rely on desalination already

There are only 3 countries that do: Bahamas, Maldives, and Malta.

Other countries that depend heavily, but not completely: Qatar, Kuwait, UAE.

Qatar, Kuwait, UAE. And these guys rent out tons of farmland in the USA to grow crops because they can flood irrigate and get five crops of alfalfa a year to feed their livestock.

Desal isn't useful for anything but a stop gap