The Pharisee position of exclusivity would have us shoot ourselves in our foot.
The very verse mentioned Romans 3: 9-20 is not the Christian position, Paul is speaking from the implications of the Pharisee standpoint.
The entire context whole chapter 3 Paul is pointing out the equality and the flaw of Pharisee position.
Romans 3
9What then? are we better
than they? No, in no wise: for we have before proved both Jews and Gentiles, that they are all under sin;
When Paul says are "WE" better than they. He's talking about WE JEWS.
All the following is JEWISH LAW these are not things introduced by Jesus:
10As it is written, There is none righteous, no, not one:
11There is none that understandeth, there is none that seeketh after God.
12They are all gone out of the way, they are together become unprofitable; there is none that doeth good, no, not one.
13Their throat
is an open sepulchre; with their tongues they have used deceit; the poison of asps
is under their lips:
14Whose mouth
is full of cursing and bitterness:
15Their feet
are swift to shed blood:
16Destruction and misery
are in their ways:
17And the way of peace have they not known:
18There is no fear of God before their eyes.
19Now we know that what things soever the law saith, it saith to them who are under the law: that every mouth may be stopped, and all the world may become guilty before God.
20Therefore by the deeds of the law there shall no flesh be justified in his sight: for by the law
is the knowledge of sin.
Paul is clear whatever the law says it applies to those under the law, that way God can hold Jews accountable and guilty before God rather then license to sin for Jews and only Gentile accountability.
The things above those things weren't written for the first time in the new testament, Those things were applied to a very misbehaving Israel.
We see Israel fail over and over and over from genesis all the way through.
The entire plot of the old testament is basically God was happy with those who do what he says, upset with those who did not.
God can annihilate absolutely every evil in the world in a blink of an eye. He can force every single creature to never sin right now snap of a finger.
Why doesn't God do this? Love, kindness, mercy, patience.
Luke 6
32“If you love those who love you, what credit is
that to you? For even sinners love those who love them.
33“If you do good to those who do good to you, what credit is
that to you? For even sinners do the same.
God is not running the universe at egomaniacs pace of my way or the highway. We already would have been done.
God's priority is the sinner. Who ever you think is the worst, least deserving of mercy, the bull's eye of God's wrath, That's God's highest priority. That's his most treasured child.
If we can't forgive them we take their place being worst. You can only love God as much as you do them.
You might declare to love someone because Jesus loves them. But the example of Jesus, what he is teaching is why Jesus loves anybody.
Why does Jesus love that "useless" sinner? You can learn this. Hint its not because he flips a coin.