Why should evangelical Christians engage the thought and experience of these early Christian witnesses? First, study of the Fathers, like any historical study, liberates us from the present. Every age has its own distinct outlook, presuppositions that remain unquestioned even by opponents. The examination of another period of thought forces us to confront our innate prejudices, which would go unnoticed otherwise. As contemporary historical theologian Carl Trueman has rightly noted:

The very alien nature of the world in which the Fathers operated challenges us to think more critically about ourselves in our own context. We may not, for example, sympathise much with radically ascetic monasticism; but when we understand it as a fourth century answer to the age old question of what a committed Christian looks like at a time when it is starting to be easy and respectable, we can at least use it as an anvil on which to hammer out our own contemporary response to such a question.

For instance, Gustaf Aulén, in his classic study of the atonement, Christus Victor, argues that an objective study of the Patristic concept of atonement will reveal a motif that has received little attention in post-Reformation Christianity: the idea of the atonement as a divine conflict and victory in which Christ fights and overcomes the evil powers of this world, under which man has been held in bondage. According to Aulén, what is commonly accepted as the New Testament doctrine of the atonement, the forensic theory of satisfaction, may in fact be a concept quite foreign to the New Testament. Whether his argument is right or not—and I think he is quite wrong—can be determined only by a fresh examination of the sources, both New Testament and Patristic.
Then, second, the Fathers can provide us with a map for the Christian life. It is indeed exhilarating to stand on the East Coast of North America, watch the Atlantic surf, hear the pound of the waves, and, if close enough, feel the salty spray. But this experience will be of little benefit in sailing to Ireland and the British Isles. For this a map is needed—a map based upon the accumulated experience of thousands of voyagers. Similarly, we need such a map for the Christian life. Experiences are fine and good, but they will not serve as a suitable foundation for our lives in Christ. To be sure, we have the divine Scriptures, an ultimately sufficient foundation for all of our needs as Christians (2 Tim. 3:16–17). But the thought of the Fathers can help us enormously in building on this foundation.
A fine example is provided by the pneumatology of Athanasius in his letters to Serapion, bishop of Thmuis. The present day has seen a resurgence of interest in the person of the Holy Spirit. This is admirable, but also fraught with danger if the Spirit is conceived of apart from Christ. Yet, Athanasius’s key insight was that “from our knowledge of the Son we may be able to have true knowledge of the Spirit.” The Spirit cannot be divorced from the Son: not only does the Son send and give the Spirit, but also the Spirit is the principle of the Christ-life within us. Many have fallen into fanatical enthusiasm because they failed to realize this basic truth: the Spirit cannot be separated from the Son.
Or consider the landmark that has been set up on the landscape of church history by the Niceno-Constantinopolitan Creed, commonly called the Nicene Creed. This document, while by no means infallible, is nevertheless a sure guide to the biblical doctrine of God. It should never be dismissed as being of no value. To do so shows a distinct lack of wisdom and discernment. I vividly recall a conversation in the 1990s with an administrator of an academic institution with which I was associated. During the conversation the subject of the Nicene Creed was raised, and this particular individual remarked cavalierly that there was no way he would be bound by a man-made document like this creed. Honestly, I was horrified by his dismissive approach and considered, and still do consider, such a statement to be the height of folly and the sure road to theological disaster.

Haykin, M. A. G. (2011). Rediscovering the Church Fathers: Who They Were and How They Shaped the Church (pp. 17–18). Crossway.