All of fleshly Israel's promises, blessings, benefits, and advantages under the old covenant could not purchase its redemption and salvation under the New.
That could only occur in Christ under the New Covenant in His Blood.
What you never seem to understand is that every Dispensationalist I ever knew about (with the exception of John Hagee, which, as I stated earlier, the rest of us do not consider a
real Dispensationalist) agrees completely with your statement I highlighted above.
The blessings promised to those who compose Israel after the flesh, were promised them
during the time of the Old Covenant, but they were not made
under the Old Covenant. Indeed, they went back much further that that, having been first made to Abraham, then to Isaac, and then to Jacob. And the Old Covenant was not instituted until the time of Moses.
The blessings promised
in the Old Covenant, as opposed to simply
during the time of the Old Covenant (which are two different things) were all conditional. While the
ancient promises, which were made
before the time of the Old Covenant, and the promises of a future restoration, that were made
during the time of the Old Covenant were unconditional. These
unconditional promises of a future restoration were made to the nation of Israel, to the two sub-nations of Judah and Ephraim, to the twelve tribes of Israel individually named, to the sons of Zadok, and to the families of the huses of David, Nathan, Levi, and Shimei.
But these
unconditional promises did not eve involve eternal salvation. They were
only about a
physical restoration of the
physical nation of Israel to its
physical ancient homeland. And to a restored
national relationship with their God
Now neither a nation nor a family can be eternally saved. As we often say in the current day, "God has no Grandchildren." Even so, even though the nation, as such, and numerous named families within that nation, will be restored to their God, the only way any
individual within that nation, or within any of those families, will receive eternal salvation is through a living, personal faith in the blood of Christ shed at Calvary.
What I have stated here is what all real Dispensationalists believe and teach. So your objection is totally invalid.
Your problem is that you do not
want to believe that this physical restoration of the nation of Israel, so very explicitly and repeatedly promised in the scriptures, will actually take place. So you rely on
your chosen interpretations of scriptures that do not actually say what you
choose to interpret them to mean. And then you use those
interpretations as an excuse for denying the
explicitly stated promises of a God who cannot lie, and who is always faithful.