Show me where Scripture claims to be complete?
But these [signs] are written, that ye might believe that Jesus is the Christ, the Son of God; and that believing ye might have life through his name.
John 20:31
That thou mightest know the certainty of those things, wherein thou hast been instructed. Luke 1:4
Moreover I will endeavour that ye may be able after my decease to have these things always in remembrance. 2 Peter 1:5 (How? Write it down and canonize it.)
For the scripture saith, Whosoever believeth on him shall not be ashamed ...
So then faith
cometh by hearing, and hearing by the word of God.
. Romans 10:1, 17 (This is a reference to why Moses wrote it down.)
Now all these things happened unto them for ensamples: and they are written for our admonition, upon whom the ends of the world are come. 1 Cor. 10:11
There is no sense in scripture that the apostles left anything necessary for salvation out. For example, the IC of Mary is de fide RC believes. As such, RC believes the apostles forgot this and that it can improve upon them. Nothing could be farther from the truth.
If your last statement is true, why such major fights in the early Church about the natures of Christ, the divinity of Christ, and so on? You think you can believe that Christ was not divine, really, and still be saved? It's not explicit to some...just ask Dan Brown.
How do you know Christ was divine? Arius arose because people denied Christ and they invented the adoption theory, thus they didn't deny God per se. The ever-virgin idea arose because of piousness over truth (Origen paraphrased). The fight about Gentile duties to the Law arose as power, prestige was lost. The ones who lost over transubstantiation were martyred. Most of the fights didn't have to do with agreeing with "it is written", but because of other ideas and motives. And remember, these fights were by bishops and priests within Christianity. Don't blame the bible for the state of men's hearts.