Why doesn’t God delight in David’s sacrifice? Why would God be displeased if David tried to offer a burnt offering (an offering completely burned up on the altar)?
David is talking about his “bloodguiltiness.” There is no offering that can take away the sin of murder. Murder requires the life of the murderer to atone for it.
That leads me to a follow-up point about the death penalty. I often get the impression that people think God amended his law so that David didn’t have to die for murdering Uriah. I don’t think so. A person cannot be convicted of a capital crime without two or three witnesses. Nobody witnessed David’s involvement. God knew of it, but presumably he always knows when someone is murdered. Nathan the prophet knew because God told him. The commander who got David’s note could have testified, but he would be only one witness. To my mind, like the situation of the woman caught in the act of adultery, David’s case is an example of the importance of credible witnesses in the Law of God. But feel free to correct me if I’m wrong.