You're nitpicking and finding something by which to reject the passage in Galatians 4. Christians, that is TRUE Christians do not have the luxury of doing that, to look for ways to explain out a verse because it contradicts what you believe. That shows me you're not honest with Scripture and therefore not honest with God and His Christ. Proverbs 30:6 comes into play here.
Saul clearly says Christ came to redeem those under the Law which means the children of Israel. God gave Moses His Law for the children of Israel because they needed it if they were going to continue to be part of the Abrahamic Covenant, a covenant that was made with Abraham and his seed. And when his seed fulfilled prophecy of going into a land that is not theirs (Egypt) God delivered that covenant people who were in the millions after 430 years and brought them out to the desert. But you know that.
Under the Law the high priest did two things: pray for the people of God in covenant and offer sacrifices for the people of God in covenant. The high priest never left the Promised Land to go to Gentiles and pray for or offer sacrifices for them. Thus, for thousands of years non-Hebrew Gentiles were unatoned and lived and died without any consideration towards their eternal resting place other than to deliver them all to "hell."
Then we have the Law written in stone implying it cannot be changed without destroying the stone it was written on. Jesus made the same declaration, that He didn't come to change the Law but to fulfill it and to obey every precept that was written in the Law of Moses. Fulfilling the Law does not mean end of the Law because Israel was still instructed and commanded to read and study the Law for instruction in righteousness so that we may be complete and thoroughly furnished unto all good works and living. So, those under the Law (Israel) as born-again followers of Christ now use the Law for their instruction in right-wise living.
Jesus Christ as High Priest did two things: He prayed for the people of God and offered Himself as sacrifice for their sin. He did not change the Law to include non-Hebrew Gentiles. Scripture cannot be broken. It can be twisted and disregarded which is what many here do when Scripture contradicts their false theology, but it cannot be broken because God's Word is unbreakable. Nothing's changed. People still reject the Word every time it contradicts their pet theories. Then we have people who are here that are not true believers. They are fake. They can be seen when Scripture contradicts what they believe instead of allowing Scripture to dictate what they are supposed to believe. In my time on forums like this I have not found or interacted with anyone that says to me, "You're right. I never knew that Scripture existed," or "Thanks for that. Now I understand more fully what we're talking about." To me people who claim Christ and reject His Word actually reject Christ Himself and their profession to Christ is a lie.
So, if the animal sacrifice was used by God to atone for the sins of Israel for one year setting up the day when God's own Son would offer Himself as the eternal and perfect sacrifice for Israel's sins forever and finally doing it, all this talk about Christ also atoning for the sins of those not in covenant is just lies, a great delusion, one that I used to believe in until the Lord opened my eyes to understand that as a God of covenant He will do all He's promised and all He has promised has been promised to Israel. So, all this talk about non-Hebrew Gentiles being in the Abrahamic, Mosaic, or New Covenants is lies. There is no Scripture teaching this lie. And no true prophet or apostle will ever say a thing that is not found in the Law, Psalms, and Prophets - Hebrew Scripture, the only Scripture that is worthy of obedience because it is the Word of God to Israel, God is their God, it is their covenant, and God has saved them to the uttermost. If there is any passage in the New Covenant writings that contradict what is written in the Hebrew Scripture, then that person who said it is a false prophet or apostle. And I do not at this time believe anything written in the New Covenant contradicts the Old Covenant. Nothing. It all comes down to interpretation, and any interpretation that contradicts the Old Covenant writings is a fake and should be rejected. So, for now enjoy the Times of the Gentiles for very soon that time will end and even now is fast coming to a close and God will turn His full attention back to Israel and fulfill all remaining covenant obligations and prophecy. Christ ascended from the Mount of Olives. He's returning a SECOND TIME to Israel and is bringing something back with Him and that is Israel's salvation for everyone who is in covenant, and they are identified as Abraham and his seed and non-Hebrew Gentiles do not come from Abraham's seed. The animal sacrifice was never given to Gentiles and since Scripture - nor covenant - can be broken, neither was the human sacrifice (Christ) given to Gentiles either.
Masel Tov.