When discussing the biblical problems with Catholic theology, it is frustratingly common for them to rush to the so-called Church Fathers to try to rescue their faith. "Oh, the Bible says this? Well, Ignatius says that, and he knew the Apostles, so I think his word carries more weight than God's word." Of course, most of them don't say it like that (although Bishop John Bell famously told William Tyndale that it is better to be without God's laws than the Pope's), but ultimately, that is the reasoning. When you use any man-written statement against scripture, you are saying man is greater than God.
But let's just leave that aside for a moment. Let's ignore the fact that even the Catholic Church acknowledges that scripture is inspired by God, and therefore more authoritative than anything any Church "Father" ever said. Let's focus entirely on the logic that because the Church Fathers (at least the early ones) knew the Apostles, they are in a position to know what the Apostles believed. What's the problem? Well, they're not alive today. So how do we know what they believed?
What we basically have here is a case of someone's interpretation of someone's interpretation of someone's interpretation (let's just pretend I said that 12 more times) of a Church Father's interpretation of the Apostles. But so-called "Protestants" have a stronger case than that. Rather than someone's interpretation (I'm not doing it again...) of the Church Fathers' interpretations of the Apostles, we have the actual writings of the Apostles themselves. The Catholic Church has a looooooong string of middle men telling them what they must believe, all while telling them they can't trust when scripture tells them something different, whereas Christians just read God's word as it is written and believe it. Catholics rely on men, Christians rely on God. I shouldn't need to explain, even to a Catholic, why that is the ultimate victory.