Not in the key cities of Shanghai and Beijing. Prime land there is scarce.

The ghost cities you read about have poor locations hence noone want to move there, they are away from the major cities, population and economic centres.

Developers selling properties in good location are doing well.

The same for Singapore. If you want to buy property, buy in growth regions such as the Jurong Lake District, Paya Lebar, Woodlands as upside potential in the longer term is good. Also must buy properties near MRT stations.