So God now has a better understanding than He did back then?
Who does God have mercy upon? Who does God forgive?
First off, how does Luke 18:16 have anything to do with wrath or mercy?
He who believes in the Son has everlasting life; and he who does not believe the Son shall not see life, but the wrath of God abides on him.
-John 3:36
That's New Testament.
For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men, who suppress the truth in unrighteousness, because what may be known of God is manifest in them, for God has shown it to them.
-Romans 1:18-19
So is that.
Let every soul be subject to the governing authorities. For there is no authority except from God, and the authorities that exist are appointed by God. Therefore whoever resists the authority resists the ordinance of God, and those who resist will bring judgment on themselves. For rulers are not a terror to good works, but to evil. Do you want to be unafraid of the authority? Do what is good, and you will have praise from the same. For he is God’s minister to you for good. But if you do evil, be afraid; for he does not bear the sword in vain; for he is God’s minister, an avenger to execute wrath on him who practices evil. Therefore you must be subject, not only because of wrath but also for conscience’ sake. For because of this you also pay taxes, for they are God’s ministers attending continually to this very thing. Render therefore to all their due: taxes to whom taxes are due, customs to whom customs, fear to whom fear, honor to whom honor.
-Romans 13:1-7
And this, too.