If they still consider their ethnicity an important factor of salvation, they have become idolaters of country over God.
They are still in the OT, OC.
And your POV wasn't?
It is eternal, but it's eternity included it's passing away at the cross of the presaged Redeemer. (Co. 2:14)
If circumcision, dietary rules, feast keeping, sabbath keeping, tithing, temple worship, days of atonement, priesthood, etc. are necessary for salvation, then the blood of Christ was not enough of a sacrifice.
Only necessary for the folks who were tricked or misguided into believing any part of the OT was still in effect.
If they accepted one part as necessary, the whole of it was necessary.
They had to elect in which Covenant they would like to live.
They couldn't live by both.
Which are you living in?