Paul poses two questions in Romans 11: Has God discarded Israel for all time? Will God graft physical Israel into the Covenant people of Abraham?
God made the New Covenant because Jacob's offspring did not have what it took to fulfill the terms of the Old Covenant. The carnal mind is hostile to God's law.
God's people are the precious jewels (or the private, personal possessions) of God, obligated to conform exclusively to His will and purpose.
We have been called for the purpose of glorifying God by totally changing our lives, conforming to His character and image.