the problem with that is "what should actually be grown" has different answers depending on whether you value profit or feeding people.

It can only be a choice between making a profit and feeding people at break-even (feeding people while losing money is not sustainable). Beyond that, the profit signal carries useful information about what the people being fed would rather eat, while keeping in line with what is economically and environmentally viable.

The problem with the current situation is that water is mispriced, and mispricing, regardless of whether it favours suppliers or consumers, makes it unsustainable in the long run.

We're also running into frequent water crises where politicians ask people to shower less while we dump 90% of the state's water on the ground.