I have ridden SF public transit of all kinds. MUNI buses are the worst, and it's not because of things that could be solved with policing. The worst part is the super high variance in door-to-door times, even if you try to plan your life around bus schedules it's bad.
If you have to take multiple forms of public transit to get where you are going, good luck. A 40 minute drive can easily be 2.5 hours on public transit if everything goes perfectly.
Also the average speed of SF MUNI buses is 8 mph, probably among the lowest in the nation. If I'm going any distance less than a 30 minute walk, it's probably going to be a better idea to walk than take the bus.