Those who were presented with the Gospel of Jesus as Messiah, and rejected that message - refusing to seek actual atonement through Jesus Christ, were/are "cut off". They will NOT inherit the promises given to Abraham - either of land or priesthood, or admittance to "the City whose builder and maker is God".
One is attached to the Olive Tree (Israel) because of belief, and is "broken off" "because of unbelief" (Romans 11:20).
If every DNA descendant of Abraham thru Jacob is/was an heir "due to being physical descendants" then Paul would not have described them as "broken off". Paul also said that God was able to "graft them in again".
Romans 11:23 "And they also, if they do not continue in unbelief, will be grafted in, for God is able to graft them in again."
When Paul wrote this verse, DNA descendants who had rejected belief in Jesus as the Christ, were NOT ATTACHED to the Olive Tree. Hence they were not regarded as Israelites in the eyes of God, so far as the promises were concerned.
It's about faith in Jesus Christ as "the only way" to God the Father. It's not about DNA. Jews could be "broken off for unbelief" and non-Hebrews could be "grafted in" for belief.