Yeah, I get where the_unbending_blade is coming from but it's not really a thing in western countries to just spontaneously make new cities, at least these days. It costs a shit ton of money and is a huge gamble. They usually grow over time due to employment opportunities in an area. There are also plenty of inland cities in California that can handle more growth, people just prefer living near the ocean and there is a lot less available space to build new cities on the California coastline.

Another option is developing multiple cores to LA and formally splitting it up into different cities. Right now, what is considered "LA" is massive, while the real heart of LA that many transplants move to is just a portion of the entire LA metro area. Formally splitting things up could pressure other parts of the metro area to develop in independently in similar ways that attracts transplants to specific areas, rather than acting as sprawling suburbs.