Yes, that is exactly what we believe God’s plan is/was, and we desperately mourn the seperations that continue to divide us, Jew and Gentile, Catholic and Protestant. This isn’t in any way meant to denigrate the Jewish faith, however, as if it is somehow “not part of God’s plan”. Unlike Protestantism, which the Church believes was a willful rejection of the unity commanded by God, modern Judaism is viewed merely as continuation of the core faith in the perceived absence of the Messiah. The seperation between Protestant and Catholic is willful and destructive, the seperation between modern Judaism and Catholicism is understandable and unfortunate. If I did not believe that the Messiah had come, I would be an Orthodox Jew without any doubt or hesitation; as a person with such a mind who believes that the Messiah has come, and that he was Jesus, I see no alternative but to be Catholic, and I am so without doubt or hesitation.
Personally I wouldn’t say that if God’s plan was adhered to that there wouldn’t be Judaism (though there definately wouldn’t be Protestantism, IMO), but rather that Judaism would now be called Catholicism. Catholic means “universal”, and what is Judaism post-Messiah other than the universal faith of all humanity united in praising God? Judaism won’t disappear after the Messiah comes, it will simply be an unnecessary and cumbersome distinction, as who will be “from Judah” and will not be?
That’s a whole study in and of itself

It’s my opinion that the Gentile converts simply began to outnumber the Jews, and they brought so many cultural elements with them that the Jewish elements were kind of drowned out, but not removed. We still have what are essentially rabbis (we call them deacons), and we have a sacrificial priesthood a la the Temple (the Protestants generally do not), in the Western Church we use unleavened bread in our commemoration of the Last Supper at every Mass, which is a Passover seder, we keep the Eucharist, which we consider the the body and blood of Jesus, in a tabernacle (the significance of this is that Jesus is regarded as literally the embodiment of the Word of God, so the connection with the Torah being kept in a tabernacle can not be overstated). Gentiles brought their own little knick-knacks into the “Universal Kingdom”, and Jewish Christians became more and more seperated from their Jewish relatives (usually not by choice, as you can see in Acts and later history), and eventually just kind of “died out”. Sadly this fed the growing perception that Jews who became Catholic were no longer Jews (though, again, in Acts you see that they tried to remain loyal to their synagogues).
As a Reform Jew I’m sure you recognize the “cutting off” that can happen within Judaism when one group doesn’t approve of another, and a kind of mutual exclusion ends up happening. The Jews who became Christian were no longer welcome in their synagogues, and over a few generations most traces of their culture die out as their children are overwhelmed by the cultural influences of the Gentiles.
From a Catholic perspective this doesn’t mean that the Church lost validity as it lost it’s more uniquely Jewish character, but any loss of legitimate cultural identity, which Jewishness certainly is, is a sad thing indeed. Most sad is that it wasn’t until this past century that the Church fully began to realize how much it had lost, and there is a growing effort within the Church by both Jews and non-Jews to dig deeply into those uniquely Jewish elements of our faith, and one of the fruits of that is what we saw in John Paul II’s efforts to reach out to Jews, and the growing identification with Mary, Jesus, and the Apostles specifically as Jews.
Unfortunately as you’ve seen on this thread, not all share my enthusiasm, though most do. Some seem to think (not on this thread) that we either hate Jews, or we hate Jesus, which is a ridiculous dicotomy. We can mourn our seperation, and hope that modern Jews will come to recognize who we earnestly believe to be their Messiah, but to put them down
as Jews is to spit in the face of God, and indeed even to spit in the face of God-as-Man who was Himself a Jew.