Is it always easy for present apologists to determine which teachings are and aren’t orthodox? Perhaps I am just blown around like a leaf in the wind too often, but I feel like sometimes things can get so confusing when you have such varying perspectives, and it’s hard to know what to think. Though, I suppose the easiest way to test the spirit and know if it’s rooted in orthodoxy or not is to look back at our long history of orthodox men and women; did any of them agree or dispute the topic in question? That is how we can today, I guess. Back then, perhaps it was more, as you are saying, from first-hand knowledge? If Jesus taught His disciples what orthodoxy looked like, and rooted them in the Christian faith, then they taught more people, and so on; I think the apologists *always* had somebody to look back at and ask questions/reflect on/with, right? Whether that was Jesus Himself or their elder or spiritual father if they used that term back then.
