"by American standards" is doing a lot of lifting. On a scale of 1 to 10 I'd give SF about a 4 compared to cities like Tokyo, Paris, Berlin, London, Amsterdam, Seoul, Singapore, ...
I don’t understand the boosters saying BART and Caltrain are good systems. When I lived there, and part of the reason I left, those systems were frequently delayed, full of drug addicts, and they lacked comprehensive service throughout SF, requiring dependence on Muni, which is worse than the other 2. I don’t think those who say this is a great system have been exposed to how other places in the world handle these things.
1. I live and work around BART stations so it works well for me
2. I just ignore the drug addicts
3. The delays are there but it all works well enough to be very useful