Well I'm glad we agree. The New Covenant of Jeremiah 31 that God makes with the House of Israel and Judah to put the Law of Moses in their hearts so they never forsake it again is the Covenant that replaces the Law Covenant God made with Israel at Mt Sinai.
The "Better" Covenant of Hebrews 8:6 is the same "everlasting" covenant God made with Abraham at Genesis 17:2-7 that he would be the "father of a multitude of nations" so that He would be "God to you and to your descendants after you," the same covenant promise God repeated to Abraham at Genesis 22:18 that "
in your seed all the nations of the earth shall be blessed," which was a repeat of the promise God made to him in Genesis 12:3 -- "And I will bless those who bless you, and the one who curses you I will curse, and
in you all the families of the earth will be blessed."
How do we know the better covenant of Hebrews 8:6 is the same covenant of Genesis 17:4 ("Behold my covenant is with you") and Genesis 22:16-18 ("By myself I have sworn")? Because Paul tells us it is the same covenant at Galatians 3:7-17 -- "Be sure that it is those who of faith who are sons of Abraham. The Scripture, foreseeing that God would justify the Gentiles by faith, preached the gospel beforehand to Abraham, saying, '
All the nations will be blessed in you [quoting Genesis 22:18].' ... Now the promises were spoken to Abraham and to his seed. He does not say, 'And to seeds,' as referring to many, but rather to one, 'And to your seed,' that is, Christ. What I am saying is this: the Law (Covenant), which came four hundred and thirty years later, does not invalidate
a covenant previously ratified by God, so as to nullify the promise."
So the Law Covenant could not invalidate the Covenant God made with Abraham that he would be the father of a multitude of nations by his Seed through whom all the nations of the earth would be blessed, but the New Covenant of Jeremiah 31
does 'replace' in a sense the Law Covenant in that God will place the Law of Moses in the hearts of the House of Israel so that they will never forsake the Law of Moses again. And that makes the point that God can make a new covenant if He wants to. And the new covenant He is talking about is the "Better" Covenant in Jesus' Blood, which isn't a "new" covenant at all, but was actually first ratified by God 430 years before the Law Covenant, when God made the promise to Abraham that all the nations of the earth would be blessed through his seed, who was revealed to be Christ when he redeemed the whole world through his blood, especially those who believe in him.
That Better Covenant is NOT the same covenant of Jeremiah 31. It is the same covenant of Genesis 12:3, Genesis 17:2-7, Genesis 22:18, Isaiah 55:1-7, Mark 14:24, Luke 22:20, Galatians 3:7-17 and Hebrews 8:6 that devolves to "all that nations of the earth" by name. NOT Jeremiah 31, which devolves only to the House of Israel, by name.