But there WERE Gentiles included from Adam to Christ. Naaman and Nebuchadnezzar are examples. There is no evidence they "kept the Law" but they certainly were believers. Nebuchadnezzar gave his personal testimony in scripture. They simply had a different set of problems but they were saved in the same fashion; through grace by faith.
What about the even bigger picture that I pointed out here?
When Abraham circumcised all the members of His house, “gentiles” were included in that covenant promise and identified with the Church.
When Moses was told to circumcise any stranger who wanted to participate in the Passover, “gentiles” were included in that covenant promise and identified with the Church (Exodus 12:). By the time Israel entered the promised land, it’s clear they are far from a genetically related group of people. Lots of “gentiles” were now part of “the Church” (Israel).
And the fact that the “land prophecy” of Ezekiel 47:21-23 included “strangers” is also evidence that “the Church” (Israel) was always intended to include gentiles.
God's people have always been identified primarily by covenant, not by race. That's the real basis for identifying Israel and the Church.
Dispensationalists miss this big picture.
If Israel and the Church have always been indistinguishable, then why are you putting bacon on your cheeseburger? Why are you worshipping on Sunday?
I didn't have time to respond to that piece but that was one of the best analysis I have read of who the true Israel is. It's very difficult to argue with logic although many do. Your reward will be in heaven.