I agree that St John Paul and Benedict did not stem the flow although they tried to. Vatican II opened Pandora’s box and once opened there was no shutting it.
It is also true that the world changed too. You say not an evil change but in fact the change was in an evil direction, the wholesale rejection of a prewar ‘christian’ moral consensus manifested by acceptance of abortion, sexual licence, promiscuity, homosexuality, divorce, etc. The Church could not possibly acquiesce in any rapprochement with these trends, JPII and BXVI did not compromise but neither did they oppose this culture vigorously enough, academically maybe but not evangelically.
By the early eighties it had become manifestly obviously that VII had not only failed in its objective of renewal but it had contributed to this failure. Retrenchment was called for but never happened, the barque was allowed to drift and I hate to say it was eventually abandoned to its fate by BXVI.