Its was just as bad 20 years ago if not worse. However at those times we did not have the proper equipment available to us measuring it. Even up to 1 year ago the Govt was issuing AQI Index based on the China Index CN AQI which is totally absurd.
Here in Bangkok they keep the Polluting busses of the roads during daytime. As soon as the sun sets those polluting busses come out to play.
They could certainly do way better however the current situation of wrong wind directions if any wind at all are not helping anybody.