It is precisely because of the Old Testament that we know the problem of mankind is sin. The Old Testament reveals in depth 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, we could not learn to have a proper relationship with God. The gospel and the New Testament would sound 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). The inspired authors of the New Testament epistles repeatedly quoted from the Old Testament. 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 (Luke 16:29-31). All Scripture is profitable for doctrine (2 Timothy 3:16).
While it is true that Christians are free from the Law, that does not make the Old Testament irrelevant to our lives. We absolutely do need to know it. So, the idea that Christians need to "unhitch" themselves from the Old Testament is not godly counsel at all.