Greetings in that Divine and Most Precious Name of Our Lord and Savior Jesus Christ!
My two cents:
Many Jews across history have converted. Countless change their names in their conversions and become locals. It is in this process that Jewish folks lose their ethnic identity and so many others opt not to convert, because up until relatively modern times conversion implied abandoning Jewish cultural and ethnic identity. In a lot of European and Western Asian societies, to be Christian was and is a kind of ethnicity of its own. So I would say then the folks who decide not to convert, be it two-thousand years ago, during the Middle Ages, or even today, do so for the same kinds of complicated sociocultural and specifically historical reasons why we still have a split between the Eastern and Oriental Orthodox.
We all know that we say many of the same things in different ways and that the things we actually disagree upon can be mutually tolerated, however the complex history of regional politics and culture clash really muddy up the relationship. We simply have too much mutual baggage in our history. I think with Jews and the Church, especially in the context of expulsions and pogroms, we just have way to much baggage for Jews to be able to settle their differences. Perhaps many feel in their heart the reverberating Truth of the Church and of Jesus Christ our Lord, however they would have to counter a lot of history to be able to take that kind of leap. We then could have a very good understanding of the Jewish perspective, both within and outside the Church, if we view them through our own familiar lenses of the relationship between Eastern and Oriental.
This is what I believe is allegorized in the passages in the Gospel which state
Large crowds were traveling with Jesus, and turning to them he said: 26 “If anyone comes to me and does not hate father and mother, wife and children, brothers and sisters—yes, even their own life—such a person cannot be my disciple.
The Church does not reject family, quite the opposite, family is quite literally Sacramental and therefore sanctified, the marriage and family bond indissoluble. However, if you are from a Jewish family and marry into a Christian family, well, there is a lot of mutual conflict there, and most of it historical, regional, local, cultural, political, and rarely actually religious.
If we let him go on like this, everyone will believe in him, and then the Romans will come and take away both our temple and our nation.”
This is also an encrypted message about conversion in the Jewish era of the Church (which lasted not just through the first, but even up until the sixth century) which speaks about the threat the Church has to Jewish ethnic and cultural identity. All of life in Jewish society is oriented around Temple/Synagogue just as ours is oriented around our parish or church. In this Gospel passage, we see that to become a Christian is perceived by the Jewish folks as a threat to their "temple and nation" and this passage was not just in the context specifically of the priestly class, but of Jewish identity in general. When Jews convert, it is a challenge to those other Jews who don't convert, and ethnic, familial, and cultural bonds and patterns shift towards to the conversion, towards to integration into the new. Converts all have a similar story, and with Jewish identity, it has simply been harder to integrate both into the Christian identity, because of the historical baggage. In many respects, political factions of Christians in history have waged outright war with Jews, sometimes mutually, sometimes vindictively, and so Jews rightfully have perceived Christians has a threat. This is that baggage which is hard for Jews to overcome in order to embrace Conversion, and I would say then that it is truly the Holy Spirit that brings anyone forward.
In the Protestant traditions, there are many popular misinterpretations of Romans 11 which have spurred an almost dangerous Christian Zionism. These folks are the ultimate Jewish apologists, in that they claim that God has preserved the distinctness of Jewish identity precisely for some kind of miraculous en masse
conversion at the Second Coming, and apparently all Jews of all history will be miraculously redeemed by the Grace of their having been ethnically Jewish. We in the Church know that the covenants with Jews were revoked, and the New Covenant of the Church is the New Israel, and the "Israel of God" which Paul mentioned. Jews within the Church are still ethnically Jews, if anything they fulfill the covenants all the more by participating in the New Covenant and the Sacramental Life of the Church. God still knows their history, their family tree, and He sanctifies them all the more by being in the Church, which was precisely sent into the world to save the Jews first, then the Gentiles. Peter to the Circumcision, Paul to the Uncircumcision, and so Jews must be a part of the Church, not outside. There is no Grace outside the Church, or rather it surely takes a lot
of Grace to find God outside of His Church