Some people misunderstand and misrepresent Paul’s doctrine concerning law. I will only address certain aspects of that here.
Paul says in Romans 3:31: “Do we then make void the law through faith? God forbid: yea, we establish the law.”
and in Romans 7:12: Paul says Wherefore the law is holy, and the commandment holy, and just, and good.”
So clearly Paul speaks of the value of the law.
One should understand that Paul’s focus in Romans is often on the relationship between the law of Moses and the law of Christ establishing that the law of Christ is superior to the law of Moses, some but not all of which is incorporated or brought forward under the law of Christ.
Paul does not intend to establish there is no sin outside of the law of Moses.
With respect to sin John says sin is the transgression of the law (1 John 3:4) and all unrighteousness is sin (1 John 5:17) so your suggestion. Also, James says if a man knows to do good and does it not regarding him it is sin (James 4:17). Paul, John, and James do not contradict; their focus is just different in those particular teachings.
The point of the New Covenant which Christ ushered in changing the law (Hebrews 7:12) is that no one (Not Moses, not you, and not I) have perfectly kept the law except for Jesus Christ, born holy from his mother’s womb not of the seed of a male but of God himself (Isaiah 7:14).
We all are engaged in spiritual warfare that shows up in the natural that none of us can escape no matter how much we wish we could. None of us knows it all. I suppose that is by God’s design less we get “big headed”. So we all should be open to a deeper, wider, and higher understanding of God’s truth.