Hebrews 10:5 Therefore, when He came into the world, He said: “Sacrifice and offering You did not desire, But a body You have prepared for Me.
These were words being attributed to David; words which were said to raise awareness of what was yet to come.
During David’s time it was quite proper to obey the laws and to make sure others did so too.
I think God was getting a bit weary with the whole sacrifice thing because He knew what was ahead and how much of a difference it would make.