Dealing with the Old Testament in Isolation from the New

In his influential popular-level book According to Plan, Graeme Goldsworthy comments on an unhappy development in Old Testament Studies:

Over the years Christian scholars have developed specialization in either Old or New Testament studies. The trend has been toward a study of the Old Testament in and of itself. This is not a Christian approach to the matter. Christians in increasing numbers have written books on the Old Testament, which hardly even mention the fact that the New Testament exists. It has become a common feature of theological and Bible college curricula that the Old Testament is dealt with in complete isolation from the New Testament. 

So he concludes: "There seems to be a failure in allowing the New Testament to determine how we relate the Old Testament to Christ."

This is lamentable. And of this tendency and failure there needs to be repentance.