A New Covenant For Covenant-Breakers
If something is not broken there is no need to fix it. But the old covenant was replaced because it was incomplete – intentionally. God's Law given through Moses identified sin and provided a system of sacrifices so that guilty people could have their sin covered (Psalm 32:1). But those sacrifices could never take the sin away (Hebrews 10:4, 11), nor change sinful desires. However the old covenant was an essential teaching tool, demonstrating that sacrifices made by penitent people would avert God's anger. But it could never make sinful people holy. It was God's plan that only Jesus could do that. Meanwhile the old covenant set the scene for all that Jesus would do.
That new covenant was not a hurried after-thought, because the old one had failed. It was planned ages before the first one was given to Moses (1 Corinthians 2:7). In so many ways it was a physical representation of the spiritual work, which Jesus would accomplish, as an architect's model demonstrates the final building. It also provided many personal and public health measures (Leviticus chapters 11-15) to protect God's people millennia before infectious diseases were understood. Also the principle of a rest day when worship would replace the focus of work – essential for physical and mental health. But getting through the year is different from getting to heaven: for that we need Jesus. Abraham understood that principle (John 8:56), as did many others who lived under the old covenant; by faith they anticipated something and someone better (Hebrews 11:13-16).
Rules cannot change our desires; they can only regulate our actions. God planned to give people a new heart - new desires and spiritual horizons – through a personal relationship with Jesus Christ. God promised to indwell His people writing His law in their hearts, giving a new desire to love, please and serve Him. Quoting from Jeremiah 31:31-34, the writer reminded the Hebrew-background believers that God had promised His new covenant more than 500 years before Christ. After Jesus' resurrection the old covenant was obsolete (Hebrews 8:13), and within 40 years Jerusalem had been sacked and the temple was destroyed. No priests, altar or sacrifices remained: but Jesus is still the Great High Priest for ever, and His blood still atones for all sin (Hebrews 10:8-10).
Rules may deter the worst of our behaviour but they can never make us good, or make us holy to be close to God. The new covenant of grace promises that sin is taken away, guilt is removed, and righteousness is given to us as the holy people of God. Live in that covenant. Don't go back to legalistic religion. Allow God's love to embrace you, confess your sin, receive His forgiveness, delight in His Word, seek His grace to desire what He desires, and work alongside Him.