Isaiah 16-18 contain oracles against three nations: Moab (remember who Moab is? from the book of Genesis, the son of Lot and his daughter!), Damascus/Syria, and Cush/Egypt. These nations at one time or another opposed God and the nation of Israel. But the cause for judgment is rooted in very common forms of evil.
Moab is guilty of pride and insolence.
Damascus is guilty of rage and idolatry.
Cush is guilty of aggression towards others and causing fear.
It is one thing when a one person has this problem, maybe a parent or child in a household. But what happens when a few people in the neighborhood unite around one of these evil acts. Or people at work come together and perpetuate all sorts of mean things/conditions upon others. It can get ugly very quickly, and ruin a lot of livess in many subtle and profound ways.
This is why Isaiah includes these oracles: Israel needs to know that God will stick up for them. Evil/wickedness/meanness will not go unpunished, justice will come.
Remember: God uses people as instruments of his justice. And sometimes God has to wait for people to wake up to their role in bringing about justice, ending the evil that fills their home, workplace, their church, etc.
Do see something at home, at work, at church, in your neighborhood that you know is just plain evil? Have you considered what you could do to bring it to an end?
The goal of God is not to destroy evil, but to redeem people from evil, to free them from the bondage of evil. But if people are unwilling to let the shackles of sin be taken off their ankles and wrists, what is God going to do? He won't force his mercy on anyone. God wants to use you to bring about the end of evil, but more then that, he wants to use you to free people from evil. Who do you know that needs freed?