"They shall ..." It is a clear fact from the Bible that God does most of His work through people. The people who are set free by Jesus will become people who build up ancient ruins and repair the devastation of many generations. We need to look at the world in hope. When God's Spirit moves in us (individually and corporately) all sorts of devastation can be undone.
There will come a time when the church fulfills its mission as the body of Christ, and the world will respect the church and come to the church for counsel. It is difficult to see how this can be given the state of our society at the moment, but that is precisely the point. Our God is a transforming God. The situation of Israel when this was given was desperate, yet sometime later Cyrus did send the exiles home to rebuild the temple. It is possible that the things spoken of here are part of the Millennium that is spoken of in Revelation.
Why will this happen? Because the Lord loves justice. Ultimately it is His zeal which will accomplish this, but the fruits of it spread to His people.
So we should rejoice before the Lord. A time will come when righteousness and praise will sprout up in the world. You may say this is impossible, it is just fantasy. But ask yourself this: who will win God or Satan? The way we see things just now is not the way they will remain. It is God's plans that will be fulfilled.