"You will say, 'Branches were broked off that I might be grafted in.' Granted. But they were broken off for unbelief and you stand by faith. So don't be highminded but fear. For if God did not spare the natural branches, neither will he spare you. Note then the kindness and severity of God severity to those who have fallen but God's kindness to you, provided you continue in his kindness, otherwise you too will be cut off. And even the others, if they do not persist in unbelief, will be grafted in again for God has the power to graft them in again." (Romans 11:19-23).
Once again we have a pretty plain message. Paul is referring to those Israelites who did not believe the gospel of Jesus Christ and so these branches were cut off from the tree of life. And he is also making this point to the Gentiles so that they themselves do not get on their high horse and be cut off from the people of God. God can cut them off just as he cut these Israelites off from the people of God.
Carefully notice the language. "Branches were broken off." Broken off from what? The answer is obvious. They were severed from the true people of God. "God did not spare the natural branches." God did not spare these Israelites. They have fallen and Paul warns the Gentiles that if they also do not abide in God's kindness they too will be cut off just like these Israelites.
There is no escaping this message without all kinds of mental gymnastics and contrived interpretations complete with a denial of the message. Paul is plain. These people of God were cut off.