We largely stopped growing avocados in the US when water rates went up. With the increased rates, and NAFTA, US avocado ranchers could not compete. There is speculation that Mexican cartels own/operate much of the Mexican avocado industry that we rely on.
I say this as someone who whole heartedly believes in desalination as a way forward, but if we refuse to embrace desalination we need to recognize the tradeoffs like you point out.
I think the problems with desalination are the cost (facilities, energy) and the leftover brine, which is damaging to the environment wherever it's dumped. It has its uses, of course, but not without drawbacks.
I've never fully understood this, shouldn't the brine be mixed in with wastewater? It's all a net-zero system, it's not like water is leaving the system.
The rest is just infrastructure (which is mostly political will).
If you are talking about using it for datacenters than that might be right, the person above is talking about farming, so they desalinate the water, the fresh water is used for crops, and the brine has to go somewhere. If you aren't really careful then dumping it back into the ocean will mess up the ocean in that area.
I say this as someone who whole heartedly believes in desalination as a way forward, but if we refuse to embrace desalination we need to recognize the tradeoffs like you point out.