Judah is confused about its identity since it had turned away from the one true God to god substitutes and pagan worship. It was truly a divided nation spiritually and doomed to failure since it lacked a clear focus on God and doing right. The consequences are the same today as then, rejection of God, lack of direction as a godless people pursue lives without purpose. The end of this without repentance and faith is spiritual death.
In verses 15-17 God accused the people of having the blood of others on their hands due to their sinfulness and wrong doing. God told them to repent and to do right, to visit folks in prisons and orphans, etc., i.e. good works.
In verses 18-20 the people's behavior is termed unreasonable sine it is sinful and not acceptable to a Holy God. God calls the people to meet with Him with a repentant heart and God will "wash them white as snow" as alternative action entirely of God's grace offered to the faithful and those "that are willing".