>A huge reason these shared spaces are so miserable is because the communities around them cannot support them. Parking minimums and low density means that not only are these commercial properties insanely expensive, but also that not enough people can access them.
That might be a small part of it, but some of the places I'm talking about have been there for 30+ years. And they were better before, when the population was even less dense than it is now. Culture plays a HUGE part in this stuff, and I think much bigger than any parking minimums or housing densities. Compare NYC at the various decades over the year to see an obvious example. There are decades where NYC would be a nice place to live if you're a urbanite, and others where it would have been absolutely miserable no matter how much you like high rise tenements.
And my personal feeling is right now the US as a whole is going through a down turn with respect to public behavior and pride, and as a result people want their own versions of these things. I think one place where density does have a factor is in being able to support multiple versions of something. You don't want your local theater servicing 10,000 people. You want the scales to be tilted more towards 100 theaters servicing 100 people each. Both for variety but also because each can serve the specific desires of a specific clientele. Part of the problem with shared spaces is you can only be so much to so many people before either you're not what they want when they want it, or you're so diluted that you're not what anyone wants.
