Six years ago, Chinese Premier Wen Jiabao cautioned that China's economy is "unstable, unbalanced, uncoordinated and unsustainable." China has since doubled down on the economic model that prompted his concern.

Mr. Wen spoke out in an attempt to change the course of an economy dangerously dependent on one lever to generate growth: heavy investment in the roads, factories and other infrastructure that have helped make China a manufacturing superpower. Then along came the 2008 global financial crisis. To keep China's...