Whenever I go to LA, it seems like an urban slum with no significant development of note (above 6 story) in most of LA. Its as though the land is worthless, even Oceanside has taller buildings than Long Beach or Riverside, and Oceanside is literally the middle of nowhere California!

With that low density style of development, your not going to be able to justify a rail line that can move 20k people an hour, as there aren't enough people who can get to a station to feed it.

I blame LA's zoning that keeps it as an urban slum. Dezone the city and you'd see areas around existing mass transit densify over the next decade.