First of all, if you ever visited China you know how occupied those "ghost cities" are, they may lack the occupancy of old cities, but they are increasing by the year.
Second, there are definitely real ghost cities, but those are in bad places, like inner Mongolia and the like. The percentage is relatively small.
The reason western propaganda keep using the same cities is because it is in fact the same cities and others have been filling up.
Third, Chinese cities is still looking to expand the population of current old cities like Dalian, my home town from 6 to 8 million people. So more will actually move to the cities in the coming decades, and once the older cities are more or less full, the new cities will start to get full.
As to demand, it's a cycle, Chinese people get higher paying jobs by building new cities, they in turn have the financial power to move into these cities. New cities are built, and businesses move in, then comes the population. For example, Dalian has a new IT area that's bring jobs and new people, that's how it works.
People can't wait for buildings, what do you want them to do in the mean time? Live on the street?
it's a loaded topic, just look at how many lives in the cities compare to 20 years ago, how many will live in the cities within the next 20 years.
Compare to India and then it's apparent what our respective policies are doing.
Don't let emotions do the talking let's look at facts.