It is precisely because of the Old Testament that we know the problem of mankind is sin. The Old Testament reveals in great detail the reason for God sending His Son into this world. Hence, it is precisely because of the Old Testament that we are able to have a correct understanding of God's love and forgiveness. Apart from the Old Testament, the gospel and the rest of the New Testament would sound strange and irrational.
The New Testament was never meant to stand independently of the Old Testament. Both were breathed out by God. The New Testament is rooted in history as is the Old. In fact, both Jesus and Paul accepted the validity of the Old Testament (Mark 10:6; 1 Corinthians 15:1-4). Paul said that the Old Testament Scriptures were written to encourage and instruct us (Romans 15:4; 1 Corinthians 10:11). The Old Testament Scriptures testify of Christ (John 5:46-47; Luke 16:29-31).
While it is true that Christians are free from the Law, that does not make the history of the Old Testament inapplicable to our lives. It does nothing to relegate its content. The Old Testament contains moral lessons that are very much relevant to us. We absolutely do need to be familiar with it. The Law reflects the righteous character of God. Consequently, the idea that Christians need to "unhitch" themselves from the Old Testament is terrible advice.