That's in large part because people don't want to buy houses now (b/c of the volatility of the SF real-estate market and a lot of people don't feel it's a safe investment). And yet people are still renting (b/c wages are high).
> San Francisco doesn't need to build high rises everywhere in the city, it needs to allow taller buildings
This is just not a longer term viable solution.
> Lots of cities in europe are filled with buildings of that height (eg paris) and it doesn't seem to hurt their quality of life too badly.
Paris a great example of where it does NOT work. You have the old center with the culture and the tourists and the traditional way of life (and yes, very very expensive real-estate). The parts that do have apartment blocks are on the outskirts and are poverty stricken monstrosities (with exceptions). People don't even consider them to be part of Paris proper.
Paris is definitely not an example of healthy development.
I concede that SF is an expensive city and lots of people can't afford it. I think that's just the new reality of the city and there isn't any viable long term way to fix it short of actively making the city less appealing to live in. I don't complain that rent in Manhattan is too high. I just don't live there. I personally can't afford to live in SF (though I grew up there and love the city), so I live elsewhere in California. But at the end of the day I don't expect SF resident to change their city to accommodate me.