"For those who live in Jerusalem and their rulers, because they did not recognize him nor understand the utterances of the prophets, which are read every Sabbath, fulfilled them by condemning him" -Acts 13:27
This verse helps us understand how we should interpret the Old Testament. I think we often mistakenly think that the Old Testament is unclear in it's object and it is our task to help it along in what it's trying to accomplish. We think it's our task to make the Messiah clear where it's not quite so obvious. Paul would disagree.
Here Paul says that the people of Israel should have recognized Jesus based on the scriptures themselves. He "looked" like the Messiah they should have been waiting for had they correctly understood the prophets. So, the fault lies not with the Old Testament, but with those who fail to meditate on it day and night.
John Sailhamer's analogy is helpful here. We often think of the New Testament as a spotlight shining back on the OT. In reality, it may be better to think of the OT as a spotlight shining on the NT giving it a context that makes sense. It provides the evidence of a Messiah that Jesus fulfills.
Acts 10:42-43 points us in the same direction: "And he commanded us to preach to the people and to testify that he is the one appointed by God to be judge of the living and the dead. 43 To him all the prophets bear witness that everyone who believes in him receives forgiveness of sins through his name.”