Yep, anyone who recognize that there was a need for lamb sacrifice in the past, but now it is no longer needed because Jesus is the final sacrifice, is applying the concept of progressive revelation.
I think the difficulty is because our bibles have an OT, followed by a blank page, and then the NT where the words of Jesus are all in red. Hence many of us have grown up accepting that all the NT are instructions to us, while the OT are instructions to the Jews.
Thus, it is understandable why many will find it difficult to accept that Gentiles do not appear in the body of Christ, until the Apostle Paul was saved by God, to bring the Gospel specifically to the Gentiles.
There is always areas in Christ where we need to grow. Paul actually witnessed always first to the Jews in an
area, by going to the synagogue then on to the gentiles. So though his heart was for gentiles, he preached to all.
What we often miss, is how big the OT is, and how much more involved and complex the stories are, linked in
with history and different social and relationship situations. To a degree the NT is simpler and more focused
on two peoples ministries, Jesus and Paul. It is also difficult to marry the idea of Jesus fulfilling the law, and
in the Spirit we also by walking in love fulfilling this.
The message that it is our hearts that need purifying is missed in much of the preaching I hear. How we love
speak, live from our hearts is a hard concept, that in our hearts dwells the Holy Spirit as a Holy temple of
the Most High. We tend to have quick focused studies 1hr long at most, and each one touches on one aspect
of the gospel. But the gospel is truly vast, involved, dynamic, and our view changes as God works in our hearts.
It is little wonder people end up finding a place of rest and try and stay there.
This forum is a classic example of what risks there are in just opening up and sharing a love of Jesus.
Rather than voices of amen, the armed soldiers appear to try and make sure you are "right" rather than engage
in this wonderful walk Jesus has called us to go with Him on.