I’m pretty sure we can find more uses for ocean salt. At the amounts we’re talking about people will find uses for it. One of the things people tend to ignore is that ocean water contains a lot more than just salt. It also contains metals and organic compounds. Looking over the Wikipedia article there is a significant component of magnesium, sulpher, calcium, potassium, and bromine. There are even industries devoted to extracting sodium, magnesium, potassium, and calcium from sea water. If we substantially increase the desalination of sea water we could significantly reduce the cost of extracting them. With the amount of brine you’re talking about it would pretty much be free to anyone who could find a use for it, since the alternative is diluting it and pumping it back into the ocean, which is pure cost. At that scale you could likely also extract trace components in significant quantities. The page mentions lithium and uranium were attempted in the past, with uranium never seeing industrial scale due to it being too expensive, but economies of scale and all that.