I live in Seoul, which has superb public transit. It can work if designed well.
Busses have their own lanes to ensure traffic minimally affects them. Bus-train transfers are well managed. High density means that mass transit ends up being faster due to traffic concerns. Speed limits are quite low, which also makes vehicle accidents less lethal.
As for prohibitively expensive, that’s only if you don’t sufficiently tax your corporations ;)
So basically, vote for local and national government that will create an environment where public transit works