The Church today senses that the Gospel has not reached modern humanity and the new structures of modern society. The Faith seems to have lost its vigour and what is needed is a new systhesis of faith and culture. The Gospel needs to enter into dialogue with culture in order to evangelise it. This is what the Second Vatican Council speaks of, laying out the broad brush strokes for the New Evangelisation.
The Council taught that dialogue between faith and culture takes place first of all in the hearts and minds of Christians, who are citizens of both the spiritual and temporal cities. But, this dialogue does not happen when Christians either do not understand the culture or do not have a sufficiently formed Christian faith. The problem today is that Western culture has been de-Christianised so much that Christians are not sufficiently evangelised themselves to be able to engage in real dialogue and to form a culture which is inspired by the Faith.
Nevertheless, the Mission of the Church is to all people, forming a communion which is a reflection of the perfect society that will exist in Heaven. The Redemption restores man's unity with God and therefore so too, the communion of the human race. Thus, catholicism declares that there is nothing in the world which is set outside the saving Mission of the Church.