Then what of the concept of a "teaching Church"? Many things that plague our modern world are not *directly* addressed by Scripture. Contraception, abortion, in vitro fertilization, cloning, nuclear war and a host of other things do *not* have anything specifically addressing their rightness or wrongness in Scripture. Sure, there are passages that can be referenced to address them (the Catholic Church does, in fact, use those passages), but there are no passages that directly deal with them. With some, such as IVF and cloning, there was absolutley no way to anticipate, 2000 years ago, the need to develop traditional teaching against them. And with all of my examples, plus, of course, many others, they are certainly crucial questions, but if, as you contend, all such crucial questions have been crystallized in Scripture, where are the citations?
There aren't any. Passages are cited by the teaching Church that merely allude to these sorts of issues, as if by derivation. The Church can adequately address them through its authority to interpret Scripture. But, clearly, not "all *crucial*" tradition has been "crystallized" in Scripture to deal with these things.
But now we're back to authority. Nothing can or will be done by the generic "Christian Church" about such things as the modern ills listed above, because it is hopelessly divided in authority. The Catholic Church, among the many, says one thing, and there can always be found another Christian denomination in opposition. And both cite scriptural passages to back their position. That's just considering two groups. In reality, there are often nearly as many positions as there are denominations. Evil triumphs in such a climate. Jesus prayed as He did in John 17, especially vv. 20-21, for good reason.