"Now he has obtained so much more excellent a ministry
as he is mediator of a better covenant,
enacted on better promises."
I don't know about you, but it's weird to think about God "improving." God is God. He's unchanging. That's kind of His thing. So what does Paul mean here when he talks about a more excellent ministry, a better covenant, and better promises.
No, I don't think this refers to some increase in God's love for us or God stumbling upon a higher form of virtue. I think this is the expression of the fullness of God's plan being reached. The covenant that Jesus has for us is a better covenant. The promises that He's made to us are better because we are not just a chosen people, but we are promised to be sons and daughters of God.
St. Athanasius said, "The Son of God became man so that we might become God." This isn't like Mormanism. This is more like marriage. In marriage, two become one flesh. The Mass is often compared to the Marriage Feast of the Lamb. In the Eucharist we experience the consummation of God's love for us. In receiving Jesus into our bodies, we become Jesus. The same is true in Baptism and in our daily work on our relationship with Him.
This opportunity that we have to really
be Christians, to live out our relationship with God with all our might, is God's more excellent ministry. This is the better covenant. These are the better promimses.