I have read all of Romans chapter 9-11 many times. Paul knows God has cast the Jews off (Romans 11) so in Romans 9 Paul refutes the arguments he knew the Jews would have in God casting them off and refutes the errors the Jews believed.
In Romans 10 and 11 Paul shows us who have always been God’s people and that being the ones who obeyed God have always been God’s people as those who obeyed by not bowing to false god Baal. The Jews would not obey Christ hence broken off and not of God’s people.