You also generate brine, you know, and that is its own environmental disaster that must be disposed of. In addition, maintenance of facilities in contact with salt water is murderously labor intensive.
Desalinization is economically useful up until you provide everybody with drinking water. Once you pass that point, desalinization is way, way, way less useful.
Most people so far don't comprehend the kind of huge change free/extremely cheap electricity would bring to the world. We have the tech to do a lot of stuff but it is not cost effective cheap electricity will change that.
Apparently seawater has 3.5% salinity. So desalinating enough to water crops/supply cities leaves you with a lot of salt.
Metals that can be extracted from seawater include:
Sodium (Na): One of the most common metals found in seawater, sodium can be extracted through solar evaporation or electrolysis.
Magnesium (Mg): A metal that can be extracted from seawater.
Calcium (Ca): A metal that can be extracted from seawater.
Potassium (K): A metal that can be extracted from seawater.
Lithium: A metal that may become more important in the future as demand for lithium batteries and fusion energy increases.
Copper: A high-value metal that is often present in seawater.
Nickel: A high-value metal that is often present in seawater.
Cobalt: A high-value metal that is often present in seawater.
The idea is that our salt would cover part of the salt dome, preventing that part of the salt dome from providing salt to the water. Instead, the salt that would have come from that part of the dome comes from our salt.