In Christianity, Scripture is the sole and sufficient authority. Not only is this a clearly taught doctrine within Scripture, it is self-evident to anyone with a basic understanding of what Scripture actually is. Put simply, the Scriptures present themselves as having been inspired by God. The word Paul uses in his epistle to Timothy is theopneustos (θεόπνευστος), which means "God breathed". In other words, setting aside the human authors of Scripture, Scripture is as reliable and authoritative as if God Himself had written it with His own quill. No mature Christian would ever dare contradict it.
Immature Christians, on the other hand, would, and very often do. The same can be said for heretics; those who claim faith in God, but in reality believe in something contrary to Him. Scripture protects us from such folly, and regular, preferably daily study and meditation on God's word is heavily encouraged throughout Scripture. But when their views do not line up with Scripture, some people have an alternative strategy. Rather than defending their views with Scripture, they instead argue from the so-called Church "Fathers".
This is obviously fallacious, for a number of reasons. Not least of these reasons is that the Church "Fathers" are not the Fathers of the Church. As a matter of fact, they are not inspired at all. Their authority extends no further than modern pastors. Their interpretations are not infallible, but merely valuable at best. Even then, they are valuable only if they line up with Scripture.
As shown in the article linked above, they very often didn't. The Church "Fathers" were often products of their times, and were just as capable of both compromise and heresy as the modern Church. Thus, using them as a foundation for our own beliefs is all but guaranteed to lead us to error.
Of course, the Church "Fathers" did have their good beliefs too. Take, for example, the issue of the Trinity. The Church "Fathers" believed and preached the doctrine of the Trinity. Here's the thing: So does Scripture. It would be absurd to base your argument for the Trinity on the beliefs of the Church "Fathers" simply because you don't need to. It might make some sense to ask why they were unanimous in their Trinitarian interpretations if Scripture is not so clear, but to do so in the absence of Scripture is positively asinine.
It is, of course, possible to use the Church "Fathers" as supplementary arguments in favor of the doctrine of the Trinity. You could even structure your argument like this: "The Church "Fathers" believed in the Trinity. Here's what the Bible says about the issue, showing they were right." But when heretics or immature Christians argue from the Church "Fathers", what it usually comes down to is "yes, the Bible appears to say X, but this/these Church "Father"/s believed Y, and so you should too".
But does this not place uninspired men above the inspired word of God? The Christian thing to do is to hold the Church "Fathers" equally accountable to the test of Scripture as the "fair minded" Bereans did with the actual Apostles in Acts 17. If even a legitimate Apostle, inspired by God to declare His mysteries, holds less authority than the Scriptures, how can any Church "Father" be immune from such a test? My Christian brethren, if you are to be fair minded, you should never take the word of a Church "Father", or even their unanimous voice (if indeed such unity could be found) as if it was Gospel. Rather, if the Church "Fathers" should enter your mind at all, it should be "they believed this, and here's why Scripture says they're right", or "they believed this, but scripture says they're wrong, and so I reject them in this case". Any other view will not only lead to you making and defending an error, but also automatically makes the error of holding the word of man in higher regard than the word of God, a sin commonly known as "blasphemy".