If you are taking a trip somewhere, what is the one essential thing you take with you? A roadmap. (or a GPS device). You need it in order to get to your destination. Without it, you are going to get lost and end up somewhere else. You need that roadmap so that you can get to your destination. Church history performs the same function. It is a roadmap. The past sheds light on the future. There is so much we can learn from those who have gone before us.
In my church tradition, we have what is known as the three pillars of Anglicanism: scripture, tradition and reason. All three are essential. Scripture is primary. Church tradition helps us understand the scriptures. We see how those who have gone before us have understood those same passages and it then helps us shape our views. Our reasoning abilities is also key but it is shaped by the first two. Church history (tradition) plays a vital role.
How should we live out our Christian faith and live according to the scriptures? How should we think about a certain issue? Church history can help answer those questions. Those who have gone before us still speak today. We just have to be willing to listen intently to what they have to say. And if you do, you will find a deep well of spiritual wisdom from which to draw from.