We will have to agree to disagree.
I know most Bible students acknowledge that the Old Testament Jews and the New Testament Jews struggled with the idea that the Gentiles would be brought into a similar relationship with the Jew. To them the Gospel stopped at Israel’s borders. Look at the only Gentile city, town or village that repented in the old covenant period – Nineveh. Jonah didn’t in any way want to bring the truth to the Gentiles. This was anathema to the Jew. Even the Jewish early Church battled with the same. Peter was given a hard time for making his move towards the Gentiles.
If everything was a full revelation in the OT why then does Colossians 1:25-27 say what it does? Paul says: "I am made a minister, according to the dispensation of God which is given to me for you, to fulfil the word of God; Even the mystery which hath been hid from ages and from generations, but now is made manifest to his saints: To whom God would make known what is the riches of the glory of this mystery among the Gentiles; which is Christ in you, the hope of glory."