After visiting San Francisco a couple of weeks ago for the first time in years, I couldn't agree more with everything you just said - especially regarding the homeless and the persistent smell of marijuana.
To add to that point further, the drug problem in San Francisco seems to be absolutely enormous. I can't even tell you the number of times I saw someone literally shooting up right on the sidewalk in broad daylight. It was very disconcerting to say the least. I get the need for access to clean syringes, but it seems to go beyond disease prevention and almost into the realm of enabling. I say all this as an expert of nothing, just my observations after 48 hours in the center of town.