In my view Heb 10 says animal sacrifice forms of worship service are no longer required after the cross "he takes away the first to establish the second".
But your post is in response to circumcision. I was pointing out that gentiles were never required to be circumcised to be saved in the OT. That is some new idea that Christian Jews came up with in Acts 15:1-2. Something that not even the non-Christian Jews were promoting.
Well the priesthood changed to the priesthood of Christ in Heb 7 and 8.
And the animal sacrifice system of worship changed to the one that we have now as far as I can tell from Heb 10:4-10
Scripture is authored by God. Moses' allowance was within the context of the civil code of that theocracy. Morally the married people were not supposed to get divorced at all - but legally in the civil codes you can't have two people that cannot tolerate each other forced to stay together until one of them dies. It is not very practical.
Jesus does not say "Moses made a mistake due to the hardness of his heart" , rather He says that the people were in such an unsaved condition in certain cases that it was too dangerous to force them to live together "due to the hardness of your heart" meaning the sinful unsaved heart of the people in those divorce-for-safety situations.