Gaudium et Spes 30
Gaudium et Spes 30 starts with a caution of no more me-and-Jesus:
Profound and rapid changes make it more necessary that no one ignoring the trend of events or drugged by laziness, content him (or her-)self with a merely individualistic morality. It grows increasingly true that the obligations of justice and love are fulfilled only if (people), contributing to the common good, according to (their) own abilities and the needs of others, also (promote and assist) the public and private institutions dedicated to bettering the conditions of human life.
The betterment of the conditions of society: a task we share not as Christians only, but also as human citizens of the planet. The council bishops also were realists:
Yet there are those who, while possessing grand and rather noble sentiments, nevertheless in reality live always as if they cared nothing for the needs of society. Many in various places even make light of social laws and precepts, and do not hesitate to resort to various frauds and deceptions in avoiding just taxes or other debts due to society. Others think little of certain norms of social life, for example those designed for the protection of health, or laws establishing speed limits; they do not even avert to the fact that by such indifference they imperil their own life and that of others.
Let everyone consider it (a) sacred obligation to esteem and observe social necessities as belonging to the primary duties of (the) modern (person). For the more unified the world becomes, the more plainly do the offices of (people) extend beyond particular groups and spread by degrees to the whole world. But this development cannot occur unless individual(s) and their associations cultivate in themselves the moral and social virtues, and promote them in society; thus, with the needed help of divine grace (people) who are truly new and artisans of a new humanity can be forthcoming.
A reiteration of a previous theme: human beings cannot hope to make substantial progress in bettering humanity without attention to virtue. For the Christian, that also means attention to the relationship with God. We believe that God makes such things possible. It is God who allows us to disentangle ourselves from the consequences of sin (not to mention human error) and thus cooperate with the divine vision of the Reign of God.