It’s a good point, but desalination has the same issue. Whenever you use seawater to produce something with almost no salt in it (be it desalinated water or crops), that means the salt has to go somewhere else. Probably in concentrated form.
Desalination may not salt the earth, but brine can create dead zones in the water. There are solutions like diluting it, and there are cases of operators who don’t care. Either way, salt is an issue if you use salt water. Has to go somewhere.