In Against Heresies, Irenaeus writes that heretics, when "...they are confuted from the Scriptures, they turn round and accuse these same Scriptures, as if they were not correct, nor of authority, and [assert] that they are ambiguous, and that the truth cannot be extracted from them by those who are ignorant of tradition. For [they allege] that the truth was not delivered by means of written documents, but by word of mouth." Even in his day, it was common practice for heretics to try to seize authority by way of tradition. The scriptures, they claimed, were insufficient; what really mattered was a connection to the early Church. In the modern day, many heretics continue this practice. Claiming a connection to the early Church, even boasting of the mythical concept of "Apostolic Succession", is common practice for a number of mutually exclusive Churches.
Ironically, this is the first clue that Apostolic Succession is a myth. Not that I'm peddling the obviously flawed logic that "you can't all be right, therefore you're all wrong". I can, however, say that any argument that cannot sustain itself against all opponents is likely invalid. To illustrate this, imagine an abortionist telling a pro-lifer "no uterus, no opinion", only for the pro-lifer to say "well actually, I have a uterus, and it works so well that I've had 5 kids". The argument may seem impactful if a woman says it to a man, but when it's said to a woman, it fails. Because it fails outside of its natural environment, it can be assumed to fail elsewhere. Similarly, when two mutually exclusive Churches argue from their equal connection to the Early Church, it becomes fairly obvious that this connection is weak.
But ironically, while many Churches claim connection to the Early Church, none of them can claim to actually be the early Church. Even those claiming to be lead by the living successors of the original Apostles cannot claim to be the Apostles. The Pope may claim to sit in Peter's chair, but who would not laugh in his face if he claimed to be Peter?
But can Peter claim to be Peter? Absolutely. So, if we find a book authored by Peter, we can reasonably assume that this book contains the beliefs of the early Church, at least as far as it was guided by Peter. "Coincidentally", this is what we do have. We do not have Peter himself, but we do have Peter's epistles. And not even this alone, we have all 66 books of scripture as they were delivered by God to the early Church.
In other words, "the early Church believed..." is about the weakest argument you could possibly make, second only to "an angel told me..." (see Galatians 1:8). The so-called "Church Fathers" (who were not the fathers of the Church) could never wield the authority of the Apostles.
Furthermore, what we find when we open the Bible is that even before the birth of Christ, the Jews were a bit of a mixed bag. They went through numerous cycles of repentance followed by apostasy followed by repentance followed by apostasy, and these cycles barely took a generation or two. When we go to the New Testament, we see a similar phenomenon. Churches set up by the Apostles themselves were riddled with errors that needed swift correction. The Galatians, it seems, were so troubled by the Judaisers, who were so audacious that they claimed authority while dismissing Paul's, that they do not seem to have actually been saved.
How, then, can we take any Church's claims about the early Church seriously? Perhaps they can find evidence that some within the early Church practiced similar practices, or held similar beliefs, but I can find evidence that some in the early Church believed one must be circumcised to be saved, that Paul was an illegitimate Apostle, that Christ did not come in real flesh, that there is no resurrection for the dead etc. Since they existed, they may have left traces, if only scant. Should such scant evidence come to light, should we therefore imitate the early Church in lieu of scripture?
Certainly not! Man is imperfect, God is not. While mostly written by the hand of men, scripture is inspired by God. Thus, unless you are so foolish as to believe God is fallible, and your Church is greater than His messengers, you will not take the view of those whom Irenaeus calls heretics. You will instead, even setting aside the explicit statements within scripture, adopt as the next logical step the doctrine of Sola Scriptura.
Rather than bickering over what the early Church may or may not have believed and practiced, what we should ask is whether they were right to believe and practice it? The way I like to put it is this: "If I search this book, will I find that religion?" With Churches claiming Apostolic Succession, the answer is universally no. That's precisely why they deny Sola Scriptura. It's because following the Bible alone, you'd never come up with their religion. You need their traditions to find their religion.
Taking the Catholic Church as the prime example, imagine you had never been exposed to the Catholic Church. When you read the Bible, would you come up with the Catholic religion? Or even half of their unique doctrines? Of course not! Most Christians go most, if not all of their lives in complete ignorance of Catholic teaching. Ask them to tell you what Catholicism teaches, they won't answer. Show them what the Catholic Church teaches, they'll balk at the blasphemies. Sometimes, all it takes for Catholics to leave the Catholic Church is to encourage them to study the Bible.
But a Catholic might try to flip this, as one recently did with me. When you open the Bible without exposure to Protestantism, will you find Protestantism? My answer was complex, but the principle is simple. See, you cannot be exposed to Protestantism without being exposed to Catholicism, because Protestantism is simply the negation of Catholicism. Yet, Christianity existed before there was a Catholic Church to protest. This is why I, personally, refuse the title "Protestant". I find it positively asinine to define what I do believe by what I don't. It makes as much sense to claim to be an atheist because I don't believe in Allah.
But if you were to study the scriptures without prior exposure, would you come up with interpretations similar to Protestantism? Certainly yes! It's easy to believe, based on the Bible, that we are saved by grace, through faith, and not of works, because the Bible explicitly says "For by grace you have been saved through faith, and that not of yourselves; it is the gift of God, not of works, lest anyone should boast." (Ephesians 2:8-9). It is easy to conclude that there is one mediator between man and God, and that this one mediator is Christ and not Mary, because the Bible explicitly says "For there is one God and one Mediator between God and men, the Man Christ Jesus, who gave Himself a ransom for all, to be testified in due time," (1 Timothy 2:5-6). It is hard to forget that the Bible makes the man of God complete and thoroughly equipped for every good work, because the Bible explicitly says "All Scripture is given by inspiration of God, and is profitable for doctrine, for reproof, for correction, for instruction in righteousness, that the man of God may be complete, thoroughly equipped for every good work." (2 Timothy 3:16-17).
Though all of this is consistent with Protestantism, it is not synonymous with Protestantism, because again, it existed before there was a Catholic Church to protest. The main message of Protestantism is basically "let's go back to that", but you cannot go back to that which you never left, and so you cannot gain Protestantism from scripture. But due to the call to return to the scriptures, Reformation-style theology can, indeed, be found in scriptures. Indeed, as I just did above, most "Protestant" beliefs can be summarised by the Bible, with minimal, if any, extra commentary.
So what are we to make of the early Church argument? Put simply, the historical argument is favored when the Biblical argument is weak. When you find a Church that is overly reliant on arguments from the early Church, all the while ignoring, or even flat out contradicting scripture, that Church is standing on shifting sand, and is due to sink below it. Christians need not worry about early Christian sources because we have access to the first Christian source. Furthermore, this source comes from God Himself, written by the hands of His very own messengers, making it the sole and sufficient authority in the Christian faith. Therefore, even if a Church can prove, with endless strings of written and authenticated documents, that a legitimate Apostle laid the very floor of its most significant meeting place, that Church is subject to the test of scripture, and should they discourage that test, they immediately fail. Only a Church that conforms its teachings to the word of God can claim to be the true Church of God, and that Church is not limited to one denomination.