The frustrating part is that it is possible. I quite enjoyed Calgary's bus system when I lived there. One bus every ten to fifteen minutes. Clean, modern, frequent, no crazies. My bus line was almost never exactly on time, but that is entirely because it had a turnaround time of something like six goddamn hours through cold suburban hell.
It's probably because it's well-funded with oil money. Fundamentally, you need a city structure that benefits bundling rides to similar destinations, and with the absurdly polycentric nature of LA that's never going to be possible.