One of the telling and accurate criticisms of the Second Vatican Council is that it suffered from an almost Pollyanna-ish optimism about human progress.
To wit, DH Paragraph 1:
A sense of the dignity of the human person has been impressing itself more and more deeply on the consciousness of contemporary man, and the demand is increasingly made that men should act on their own judgment, enjoying and making use of a responsible freedom, not driven by coercion but motivated by a sense of duty.
Perhaps in 1965, in certain parts of the West. Perhaps. But far from prevalent (e.g., the Communist world), and not for long even in the West. Contemporary man's bestial side came roaring to the surface, and the descent to the depths began.