If the Israelites had recognized and received Jesus, THIS would have atoned symbolically for the sin of Adam and Eve, who rejected God's word. Unity with Jesus was the necessary offering (obedience).

Some of Israel did believe. The Jewish religion rejected him and sought to kill him from the beginning of his ministry. Jesus brought the kingdom with Him, and sent the kingdom to all mankind by faith in His life and reign. There was not another option. The only way to have the kingdom on earth was with the king in heaven and his church ascended to him in the heavens through the Holy Spirit. The death was required so the life could be magnified. Faith in the life and reign of Jesus Christ brings the kingdom of God and Christ to all mankind.