Mostly correct. We have to understand that Israel being sidelined was a cataclysmic event for believers. Had God's word failed? Is the promise that Israel will be a blessing to the world abrogated?
Not so. Not all Israel is Israel. The Israel of God is identified not by circumcision, but by the affinity with Abraham, faith. Ethnic Israel is hardened SO that Gentiles can be included, as predestined. Then why does God blame Israel if it was predestined that she will be the fall guy in order for the latter's inclusion? Because it's God's prerogative. He will have mercy on whomever He wishes to have mercy, to withdraw it as it was withdrawn from Pharaoh, and hardening applied.
But the hardening is only temporary. If the grafting in of Gentiles resulted in the redemption of the living, the regrafting of Israel will surely result in the redemption of the dead! Such a huge topic!
That is the gist of the rebuke of the uppity gentile leaders of the church in Rome.
The rebuke to the Jewish returnees is that they were never chosen because of having met the requirements needed to be called God's People. The conscience Gentiles had was the equivalent of the law. Those with the law would be judged affording to the law, those without the law would be judged without the law.
To both, the rebuke is : all are saved by grace through faith and even that is a gift, lest any should boast. There is no group righteous, all, both Gentile and Jew have sinned, fallen short of the requirement to be deserving of the sobriquet, God's People. It is only leniency, grace, ignoring of the actual requirements, that allowed both groups in.