Glue, yes we are densely populated, but that is not the problem. 15,000 Hong Kong Chinese in a square mile is fine because they have developed a vibrant city mentality as only they can. Hong Kong works, New York works. Put us on the plains of Montana and we will wither and die.
Indeed I would prefer to live at this population density with this ethnicity that most any other that I can think of.
The problem is pollution, air, noise and water. We are constrained by a government that cannot act to reduce these because they are in the financial hands of the very people who produce the pollution.
Eventually the developing and innovative pollution laws of China will be enacted in Hong Kong but that does not have to be the case until 2047.
Until then, hold your breath and when your kid gets asthma, get out.