Sin and human nature affect everyone in society—from king to commoner—but God has covered sin from every angle in the sacrifice of His Son, fulfilling Leviticus 4-5.
Jesus' perfect offering of Himself for us fulfilled the sin offering of Leviticus 4. Our acceptance of His offering for atonement puts us under obligation.
The Messianic prophecy in Isaiah 53, plus the testimony of Peter and the author of Hebrews, show that Jesus fulfilled the azazel goat's role by bearing sin.
Hebrews 10:9 does not say that God's law or the Old Covenant has been done away, but that the system of animal sacrifices has been set aside for now.