I would argue that there is a case for accepting that western civilisation is post Christian and in terminal decline, and that rather than tryThat sentence seems to encapsulate a basic confusion amongst many believers today.
to redeem society we should instead concentrate on preaching the Gospel of repentance
According to Jesus' plan and program, announced in the Great Commission, the nations are to become his disciples - through the preaching of the gospel and then the teaching of all things which he commanded. There will be much suffering and discouragement and disappointment; but fear not, because Jesus himself has promised to be with his people until the task is done.
Thus, the teaching of the gospel - the good news that Jesus himself is the living Lord who died on the cross and rose again to receive all authority in heaven and earth, the one who graciously offers us life in his new creation - is the basic tool for bringing about his purposes on earth. Not the labours of a sinless man; not the obedience of a hard-hearted people; but a Spirit-filled community who continually die and rise in union with Christ. As believers unpack the implications of the gospel, learning to obey all that Jesus taught, the world changes. That's actually what's been happening the last 2000 years. Through their faithful and patient sufferings as they take up the way of the cross, they (or rather Jesus in and through them) achieve what the first Adam never could, and which Israel under the law never could. They bring light to the nations, and bring the earth once again under the good rule of God, bringing joyful, heartfelt obedience to every place where they are led.
The above sentence which I've quoted seems to envisage something else. It seems to see the preaching of the gospel as a tool for something other than the putting-right-again of God's creation. Perhaps just the filling of the life-boats until something better comes along. Not creation renewed, but creation replaced. We give up on God's creation, and plan instead just to squirrel a remnant out of it before it is destroyed. Conversely, the quote seems to imply that "we" have been trying to redeem society, using some other tool other than the gospel preached and obeyed. I'm not sure what tool that is in the writer's mind, but it seems to be some kind of political action... but not a political action based firstly and foremostly upon the proclaimed fact that Jesus died and rose and now reigns from the throne-room of the universe. Politics played not according to Jesus' rules (patient, obedient suffering and proclamation of his Lordship), but according to the world's rules (the way of Machiavelli).
Too many believers have a basically Gnostic view of creation. Creation (in this view) is something lesser, something evil, something that we hope to escape from. It's just a waiting area until something other arrives. The second coming does not mean creation restored and renewed, but creation replaced. This leads to the above radical dichotomy between political action and gospel preaching. Two different things for different ends. But once you've grasped the Biblical view, the above phrase will strike you the same as if a man said "let's give up on trying to grow healthy fruit, and just concentrate instead on planting seeds". Huh?
The gospel does not dichotomise in this way. It is holistic. The lines of debate about the relationship between gospel preaching and social action often rather confuses me - not because I'm a liberal who thinks that the two are the same, but because I'm a Biblical Christian who thinks that Jesus owns everything, now, and that the saints are taking the rule through praying, obeying and suffering together with him.