Well, a "new" and better covenant than which: Mosaic or Abrahamic?
The way some of you pose this debate sounds like things were better under Abraham, somehow got worse under Moses, and then got back to Abraham when Jesus came. It's as if Redemptive-Historical theology isn't even a thing.
I'm sorry but it is frankly astonishing to me that any Christian would not see that God's people in the New Covenant, even if you believe in the one covenant/two administrations view, have things better than Abraham.
As New Covenant believers:
1) You have fullness of revelation in Christ which Abraham did not have
Long ago, at many times and in many ways, God spoke to our fathers by the prophets, 2 but in these last days he has spoken to us by his Son, whom he appointed the heir of all things, through whom also he created the world.
The Holy Bible: English Standard Version (Wheaton, IL: Crossway Bibles, 2016), Heb 1:1–2.
2) You have a better high priest who has offered his sacrifice and is now interceding in heaven. No high priest had been instituted under the Abrahamic Covenant. Furthermore, you understand the significance of the role of the high priest, his sacrifice, and his intercession in a way Abraham never did.
3) You benefit from the foundational ministries of all the apostles and prophets who had not come in Abraham's time.
4) You understand the significance of the Old Covenant types and shadows in a way that hand't yet been revealed to Abraham.
5) You see the fullness of the promises offered to Abraham as fulfilled in Christ.
6) You have more of God's promises revealed since the time of Abraham.
7) You have received the command, and get to participate, in the Great Commission which was not given to Abraham but merely given as a promise to bless the world thorugh Abraham's offspring (Christ and us as Abraham's offspring through faith in Christ).
That should be enough for now.