If the extent of the human condition were to end at man being total corrupted by sin it would indeed be bad news. However, the good news that gives the gospel its name gives all mankind hope. All the sin that is rightfully ours deserves justice. In fact, justice demands it. God, who is just in nature, cannot simply ignore sin forever. He must deal with it and deal with it justly. As Paul says in Romans 3:21:26:
But now the righteousness of God has been manifested apart from the law, although the Law and the Prophets bear witness to it—the righteousness of God through faith in Jesus Christ for all who believe. For there is no distinction: for all have sinned and fall short of the glory of God, and are justified by his grace as a gift, through the redemption that is in Christ Jesus, whom God put forward as a propitiation by his blood, to be received by faith. This was to show God’s righteousness, because in his divine forbearance he had passed over former sins. It was to show his righteousness at the present time, so that he might be just and the justifier of the one who has faith in Jesus.
God’s answer to the problem of sin was substitutionary atonement; the transactionary process by which the sins of the elect are imputed to Christ on the cross, and the righteousness of Christ is imputed to the elect.
Those believers in the Old Testament had their sins passed over and they looked forward to the day of the cross and the atonement for their sins. In the same way, we look back on the actual event of the atonement and enjoy the blessing of redemption accomplished. Because of this, justification is possible. In the courtroom of God, sinners, by faith in the finished work of Christ, are declared righteous. Because Christ received our sin and was condemned on our account, we receive Christ’s righteousness and are accepted on his account.