How has God's focus changed from Jews to Gentiles between the Old and New Testaments?
In the Old Testament, God’s dealings were primarily with Israel—Jew only, with a few Gentile exceptions. After the cross, that arrangement is inverted: the gospel now goes primarily to Gentiles—practically Gentile only, with a few Jewish exceptions. Gentiles once far off are made nigh by the blood of Christ, not by coming under Judaism.
Les explains that Gentiles were once without Christ, aliens from the commonwealth of Israel, strangers from the covenants of promise, and having no hope without God in this world. But now in Christ Jesus, those who were far off are made nigh by the blood of Christ—not by entering a covenant relationship and not by coming under Judaism. He says the whole thing has been totally inverted: whereas the Old Testament was Jew only with a few Gentile exceptions, now it is practically Gentile only with a few Jewish exceptions. Isaiah was bold, saying God was found by those who sought Him not and was made manifest to those who asked not after Him—the Gentiles, who were saturated in paganism and not concerned about Israel’s God. Yet God sent the Apostle Paul to those very people. This fulfills Scripture’s basic rule that no one, beginning with Adam and Eve, ever seeks God.