Hebrews 10:9
9 Then said he, Lo, I come to do thy will, O God. He taketh away the first, that he may establish the second.
The point being made is that the First/Old Covenant cannot be taken away to establish the Second/New Covenant if the First/Old Covenant is not practiced. Due to Adam's inheritance it Must be practiced.
Jesus was the one that practiced, and fulfilled, the law.
Romans 9:30-32. 'What shall we say then? That the Gentiles, which followed not after righteousness, have attained to righteousness, even the righteousness which is of faith.
But lsrael, which followed after the law of righteousness, hath not attained to the law of righteousness.
Whereof? Because
they sought it not by faith, but as it were by the works of the law. For they stumbled at that stumblingstone;'
The covenant that preceded the Mosaic covenant was a covenant of faith, and it was Abraham to whom faith was counted as righteousness [Genesis 15:6]. It is no different for Gentiles. Gentiles do not need to follow the law of Moses as a preparation for receiving Christ. They simply accept the Spirit of righteousness by grace. Gentiles recognise that it was Jesus, a Jew, who fulfilled the law.