Are you really this confused? If the New Covenant promised to the nation of Israel is now in force then the following prophecy would already be fulfilled:
"Behold, the days come, saith the LORD, that I will make a new covenant with the house of Israel, and with the house of Judah: Not according to the covenant that I made with their fathers in the day that I took them by the hand to bring them out of the land of Egypt; which my covenant they brake, although I was an husband unto them, saith the LORD: But this shall be the covenant that I will make with the house of Israel; After those days, saith the LORD, I will put my law in their inward parts, and write it in their hearts; and will be their God, and they shall be my people. And they shall teach no more every man his neighbour, and every man his brother, saying, Know the LORD: for they shall all know me, from the least of them unto the greatest of them, saith the LORD: for I will forgive their iniquity, and I will remember their sin no more" (Jer.31:31-34).
We can know that the house of Israel and house of Judah mentioned in these verses are made up of the physical descendants of Abraham, Isaac and Jacob. That is because their "fathers" are described as being the ones who the LORD brought out of Egypt and broke the covenant and it was the physical descendants of Abraham, Isaac and Jacob who did that!
And if the New Covenant spoken of in this passage was fulfilled now then all of the physical descendants of Abraham, Isaac and Jacob would know the LORD now and all of them would be saved and will have had their sins forgiven.
That certainly has not yet happened! It will in the future and when Paul wrote his epistle to the Romans he placed the fulfillment of the New Covenant in the future:
"And so all Israel shall be saved: as it is written, There shall come out of Sion the Deliverer, and shall turn away ungodliness from Jacob: For this is my covenant unto them, when I shall take away their sins" (Ro.11:26-27).