The new covenant was also given to Israel and Judah, not the gentiles:
Heb 8:8 For finding fault with them, He says, "BEHOLD, DAYS ARE COMING, SAYS THE LORD, WHEN I WILL EFFECT A NEW COVENANT WITH THE HOUSE OF ISRAEL AND WITH THE HOUSE OF JUDAH;
Heb 8:9 NOT LIKE THE COVENANT WHICH I MADE WITH THEIR FATHERS ON THE DAY WHEN I TOOK THEM BY THE HAND TO LEAD THEM OUT OF THE LAND OF EGYPT; FOR THEY DID NOT CONTINUE IN MY COVENANT, AND I DID NOT CARE FOR THEM, SAYS THE LORD.
Heb 8:10 "FOR THIS IS THE COVENANT THAT I WILL MAKE WITH THE HOUSE OF ISRAEL AFTER THOSE DAYS, SAYS THE LORD: I WILL PUT MY LAWS INTO THEIR MINDS, AND I WILL WRITE THEM ON THEIR HEARTS. AND I WILL BE THEIR GOD, AND THEY SHALL BE MY PEOPLE.
Biblically the new covenant is only for the house of Israel and the house of Judah.
Would you advance the argument that gentiles aren't under the new covenant? Or do you suppose there's something that includes gentiles in the new covenant? And that somehow the ten commandments carried forth into the new covenant?
In the church of the Body of Christ there is no Jew nor Gentile.
Paul established that the Gentile believers need not convert of Judaism, nor do the have to follow the customs of the Jews.
So that is right, I said that the 10 commandments are not part of Christian doctrine. They were given to Moses and the children of Isreal, not to the Church of the Body.
Obeying the law for righteousness obligates one to follow the whole law.