Judaism is not a salvific way of life.
In Acts 21:20, they were rejoicing that tens of thousands of Jews were coming to faith who were all zealous for the Torah, which is in accordance with believing in what Jesus accomplished through the cross (Titus 2:14), so Jews coming to faith in Christ were not ceasing to practice Judaism. This means there was a period of time between the resurrection of Jesus and the inclusion of Gentiles in Acts 10 during which all Christians were Torah observant Jews, so Christianity at its origin was the form of Judaism that recognized Jesus as the Messiah, which means that to deny that Judaism is a salvific way of life is to deny that Christianity is a salvific way of life. Our salvation is from sin (Matthew 1:21) and it is by the Torah that we have knowledge of what sin is (Romans 3:20), so living in obedience to Torah is the only salvific way of life, which is Judaism.
In John 4:22, Jesus said that salvation is of the Jews, but if Judaism were not a salvific way of life, then that would mean that none of the Jews in the OT were saved. In Psalms 119:29-30, he wanted to put false ways far from him, for God to be gracious to him by teaching him to obey the Torah, and he chose the way of faith by setting it before him, so this has always been the one and only way of salvation by grace through faith. In Exodus 33:13, Moses wanted God to be gracious to him by teaching him to walk in His way that he and Israel might know Him, and in Matthew 7:23, Jesus said that he would tell those who are workers of lawlessness to depart from him because he never knew them, so knowing God and Jesus is the goal of the Torah, which is eternal life (John 17:3), which again is salvation by grace through faith, which is also why Jesus said that the way to inherit eternal life is by obeying God's commandments (Matthew 19:17, Luke 10:25-28).
The Messiah has come, and those who do not recognize Him now will be nevertheless reliant upon His mercy on the last day.
Again, Acts 21:20 reports that tens of thousands of Jews were coming to faith in Messiah. Judaism teaches to believe in the Messiah, so the issue is recognizing who he is.
"In the town of Berditchev, there was a proud, self-proclaimed atheist who shared with anyone who would listen his problems with a cruel, uncaring God. The great Chassidic Master Rebbe Levi Yitzchak approached him. After the atheist vociferously explained why he doesn’t believe in God, Reb Levi Yitzchak turned to him and said, “You know, the God you don’t believe in, I don’t believe in him either.”"
Many Christians present the Messiah to Jews as someone who did away with the Torah, however, in Deuteronomy 13:1-5, the way that God instructed His people to determine that someone is a false prophet who is not speaking for Him was if they taught against obeying the Torah, so if Jesus had done that, then Jews who rejected him as a false prophet for that reason would have been correctly doing what God instructed them to do, so Jews should not be blamed for rejecting a Messiah that as been falsely presented to them.
The Son is the radiance of God's glory and the exact image of His nature, so he is the embodiment of holiness, righteousness, goodness, justice, mercy, faithfulness, love, joy, peace, patience, kindness, gentleness, self-control, and other aspects of God's character, and Jews believe in embodying God's character in obedience to the Torah, which is the only salvific way of life. The way to worship the Father is by embodying His character in obedience to the Torah, which is identical to the way to worship the Son, so I don't seek a good reason to doubt the salvation of Jews who worship the Father.
So we would do better to recognize Him now, rather than spend our lives being frivolous with our eternity because we are enamored (well, some of us are) with all the 'cool' or 'spiritual' stuff we see in Judaism. I think this attraction to Judaism or Jewish culture among most Christians who display it is a tacit (and no doubt subconscious) acknowledgement that they cannot identify (with) any other culture they see in the scriptures. This is a cause for sorrow, not jubilation over blowing the shofar or pronouncing Hebrew words correctly or whatever nonsense.
Again, Jesus said that obedience to the greatest two commandments is the way to inherit eternal life (Luke 10:25-28), so Jews who are doing that are not being frivolous with their eternity, but just the opposite. Understanding the Jewish cultural and historical context of the NT is vital to correctly understanding it.