I do admit that I do not see any need for two separate good newses.
Whether you think there is a need is of no consequence.
Paul tells us there are other gospels than the one he preaches. Gal 1:8, 2 Cor 11:4
I believe wholly in a spiritual Israel
You can believe it till the cows come home, and it still won't change the fact that GOD made promises and covenant with a literal physical earthly Israel about an earthly kingdom with an earthly throne in which their Messiah will rule on earth in the very land it was promised to take place.
Isn't it repeatedly written that there is no difference in Jew and gentile? So why would there need to be two different messages?
It's repeated in Paul's gospel because Paul's gospel is not about the kingdom of Israel.
But scripture also repeatedly tells us that the nation/kingdom of Israel is elect, chosen nation with specific land to inherit and specific promises made to that were not promised to other nations.
And one of the things those Gentiles had to do to join the nation of Israel was to be circumcised. A physical earthly fleshly circumcision.
No fleshly circumcision required in Paul's gospel.
I'm not quite getting it.
All ya gotta do is recognize things that differ. While there may be some overlapping similarities at times, it's those things that differ that makes them separate from each other.
Thus, things that differ are not the same.
When one starts to recognize the differences, and that GOD is not yet through with the nation of Israel, then one can drop all the vain attempts and jumping through hoops with theological gymnastics to try and force Paul's gospel to line up previous ones. They stand on their own and do not need to be mixed at all.