I agree that the lack of employment centers is a problem but the first obstacle is the lack of demand. If more people wanted a subway than 8 more lanes on I-5, then we would get the subway. I still say that not enough people have experienced great public transit so don’t know what they’re missing.
The lack of employment centers is workable. Even in the best public transit cities people combine two or three modes to get where they are going (plus walking a block or more).
Riders need a system they can depend on at all hours of the day, a system that is reliable, flexable, and safe.
I think it also has to be good enough that people can get rid of the extra cars. The best incentive for that would be to make it free. Make the public an offer it can’t refuse.