The Calvies never have figured this one out. They did conjure up all manner of nonsense about it though.I believe Romans 3 is presenting a universal description of mankind in its natural, unregenerate state. When Paul says, “there is none righteous, no, not one” and “there is none that understandeth, there is none that seeketh after God,” he is not describing only a certain kind of person. He is summarizing the spiritual condition of the entire human race before the grace of God intervenes. Paul supports this by quoting Psalm 53. Some point to Psalm 53:1 and argue that the psalm refers only to “the fool” who says in his heart, “There is no God,” but the psalm itself immediately broadens its scope. Verse 2 says that God looks down from heaven upon “the children of men” to see if any truly understand or seek Him, and verse 3 declares, “Every one of them is gone back; they are altogether become filthy; there is none that doeth good, no, not one.” That language is universal and cannot be restricted to atheists.
Paul’s conclusion in Romans 3 makes this even clearer. After quoting these passages, he states that his purpose is “that every mouth may be stopped, and all the world may become guilty before God” (Romans 3:19). If the statements in Romans 3 applied only to atheists or only to certain individuals, his conclusion about the guilt of “all the world” would make no sense. This shows that Romans 3:10–11 applies to everyone, but specifically to their condition before salvation. For the believer, these verses describe the former life, when he was spiritually blind, enslaved to sin, and walking according to the course of this world. And naturally, the same description applies to all unbelievers who remain in that fallen condition and ultimately die rejecting their Messiah. Romans 3 is not identifying a narrow subgroup of humanity. It is identifying the natural spiritual condition of every person apart from Christ.
However, there are many Calvinists who will say that Romans 3:10-11 still applies to the life of the believer even after they are saved and born again (Which is not true). Meaning, there are Calvinists (not all of them) who will say that they sin 24/7. While believers can struggle with sin and stumble, that is not how they are characterized in Scripture. They are called "saints" for a reason. Scripture tells us to be ye holy as He is. Yet, many Christians who believe those verses on living righteously are mocked today by other Christians. They boast in how they are sinners saved by grace. Meaning, they think they can willfully continue to do evil and be in God's good graces all because they have a belief alone on Jesus. This is not what the Bible teaches even remotely.
And just think......all that they had to do is keep reading the rest of the chapter....
[Rom 3:19 KJV]
Now 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.
[Rom 3:20 KJV]
***Therefore*** by the deeds of the law there shall no flesh be justified in his sight: for by the law [is] the knowledge of sin.
[Rom 3:21 KJV]
***But now*** the righteousness of God without the law is manifested, being witnessed by the law and the prophets;
[Rom 3:22 KJV]
Even the righteousness of God [which is] by faith of Jesus Christ unto all and upon all them that believe: for there is no difference:
[Rom 3:23 KJV]
For all have sinned, and come short of the glory of God;
[Rom 3:24 KJV]
Being justified freely by his grace through the redemption that is in Christ Jesus: