I worked for a desalination company in the 1980s. From then until a few years ago, I would have disagreed with your assertion. Some recent advances have me rethinking that, however.
I'm fairly skeptical of massively expanding existing RO operations due to how we tend to handle brine - which (from what I've seen) is usually just dumping it in the general area we pump from.
However my past concerns for altering seawater on a planetwide scale are much abated. Rising sea levels and glacier melt have put an end to that.
Can't we just have giant "salt plains" where we allow the brine to evaporate and we just collect the remaining salt/minerals?
Maybe I'm crazy or not informed enough, but I always thought this water-desalination thing was a solved problem. Then I got confused when they talked about how there is "brine waste" and it's a huge ecological problem. Why do they stop short of full evaporation of the brine?
https://singularityhub.com/2019/06/18/inching-towards-abunda...