Los Angeles is an extreme case, but air pollution remains an urban problem. Emissions have been reduced, not eliminated.
It can still be a problem without being so visible as to limit your vision to less than a city block while the infirm non-hyperbolically suffocate to death.
I live about sixty miles east, and a mile above, Los Angeles. There’s a few spots on the road to my house that have a direct line of sight to the DTLA skyscrapers. Which I can actually see approximately 5 days a year, when specific wind conditions blow away all the smog.
The sky’s certainly less brown than it used to be, but it’s still brown.
Los Angeles is an extreme case, but air pollution remains an urban problem. Emissions have been reduced, not eliminated.
It can still be a problem without being so visible as to limit your vision to less than a city block while the infirm non-hyperbolically suffocate to death.