I see this movie as a commentary on the new morality in Beijing brought on by modernization. This modernization could not have happened unless there was a mobile work force so the government made a conscious effort to diminish the familial bonds. How else could a worker travel thousands of miles to Beijing or Shenzen to find work? Money had to become of greater importance. The other modernization was that men could only legally marry one woman. In previous times, men would take another wife. In previous times, families would buy children.
With these two changes to Chinese society, this movie could ensue. An Kun and Liu can now be in Beijing. Lin Dong and Wang Mei would be childless. The lust, heartbreak, the anguish, the loathing, all results. The viewer is left with the question whether the new morality is better than the old. I think the writers preferred the old.