G-d’s promises were made (for the most part, and specifically the one I referenced in Genesis 12:3) to Abraham, Isaac and/or Jacob BASED ON THEIR ACTIONS DURING THEIR LIVES, and were clearly intended to be forever, to inure to ALL of their descendants. Since it was G-d making those promises, and He does not lie like humans, and he knows the future perfectly, it is not only a covenant forever, but it is both logically and theologically ABSURD that He would withdraw His promises. That simply CAN’T happen.
The promises of God to Israel were all contingent on their obedience, otherwise you would be utterly destroyed, scattered across the 4 corners of the Earth. Hence the Babylonian captivity, and, again, the wrath of God as predicted by Jesus Christ on Jerusalem and the Temple in 70AD on the anniversary of the destruction of the previous temple, leaving some 2 or 3 million Jews dead, and many more sold into slavery. And since that time you've known no prophet, but just dozens of false "Messiahs" whom you've all flocked to, only to be disappointed again and again. And since that time you've mingled your so-called religion with the filth of witchcraft and near constant stupidities from your Rabbis, who teach you how to eat urinal cakes or that you should not pee immediately before sex, lest your children catch epilepsy.
Jesus Christ did what Israel (according to the flesh) could never do-- He kept the law, and through Him all those joined to Him enjoy the promises and love of God:
Gal 3:29 And if ye be Christ's, then are ye Abraham's seed, and heirs according to the promise.