Desalinization just makes the remaining seawater more salty. There are practical limits to this, just like there are to extracting fossil fuels from the earth.

This little device won't make much of a dent, obviously, but we've to implement better, more sustainable solutions to water scarcity, which is a manmade phenomenon.

https://medium.com/the-new-climate/i-wrote-a-book-about-water-heres-what-i-learned-cddf7e2e7dd0