It's amazing how little has changed in recent years in LA. The massive downzoning of the 1980s had its effect: prevent efficient land use, and channel money into the hands of landlords and homeowners from all newcomers. LA is a ridiculously unaffordable place to live, not because it's nice, but because of an artificial shortage of built space, due to a monopoly on the permission to build.
There is also a completely unreasonable shortage of water for a much bigger city.
And all that it takes to turn seawater into potable freshwater is energy.
We don't have a water problem. We have an energy problem.
For all of LA County, it would take 500–750 MW each year to use seawater for all our freshwater needs.
Or put another, with a single nuclear power plant, we would solve all LA's freshwater needs -- forever.