At the time of filming this movie, Mainland China was still actively undergoing the construction of a socialist society. Feudalist thought and structures were slowly wearing away, and the genuine belief that capitalism would be destroyed was nearly universal. No one would say that the era of Chairman Mao was perfect, but said era's building of communism and eradication of feudal ideas was completely genuine (something nearly anyone you ask in China today would wholeheartedly agree with, by the way). Moreover, one need only look to Hong Kong and Taiwan to see that The People's Republic of China's progress was both genuine in its execution, and in its efforts being for the people. In those days, Hong Kong and Taiwan, despite being in the then-modern 1970s, bore no similarities to any good or "modern" country, but rather shared many features with feudalist societies we think of as only existing in the past.
This story's setting and themes act as warnings to us all: even though there are no perfect places in this world, there are still those that are at least relatively fair. The development of places like Hong Kong and Taiwan in these times was not for the benefit of the people, but for that of capital, and for imperialist and colonialist countries. The film makes it almost too obvious for us: all of the enemies in this film are stand-ins for the cruel and exploitative relations throughout feudal China, with some modern capitalist elements thrown in for good measure. The workers only exist serve the upper class, and it is the intrinsic right of said upper class to exploit the laborers under them. As the film shows, when the workers are of no use to the feudal-capitalist class, they get thrown out on the street coldly.
Thematically, we're repeatedly drawn to the importance of workers uniting together, and for the importance of those with strength to protect the workers who are weaker than they are. If one has committed misdeeds in the past, serving and sacrificing oneself for one's fellow workers can be a road to redemption. In the film, workers, including women, unite to unite against their modern-day feudal lords. These are the principles and ideas of communism in action, and the movie tells us in no uncertain terms that this is the only way to build a fair society free of exploitation. The alternative to such efforts is grim.