God is the perfect teacher, and trains us in a manner that will make real, lasting changes to our character. That learning process requires that we learn much for ourselves, rather than simply reading it from a book or hearing it from a preacher. What we hear or read can inspire us, but what we learn for ourselves truly changes us.
Perhaps most critically, God holds us accountable for what we know. Those that do not understand a principle are not condemned for failing to live that principle. Such ignorance is NOT bliss, because ignorance also means a lack of joy or happiness as a result of living that principle. However, if we were given all knowledge that God has, all at once, we could not handle it. By "not handle it," I mean we could not live up to the high standard of knowledge we'd have, and we would be constantly under heavy condemnation as a result. To one group, he put it this way:
"Ye call upon my name for revelations, and I give them unto you; and inasmuch as ye keep not my sayings, which I give unto you, ye become transgressors; and justice and judgment are the penalty which is affixed unto my law."
Thus, our ignorance is a blessing of a loving God. Not that he wants to keep things from us--quite the opposite. But in his infinite wisdom and kindness he only reveals to us that which we are capable of living up to. Inasmuch as we are faithful to what we do know, he then adds to our knowledge little by little: "line upon line, precept upon precept, here a little and there a little."
How much knowledge is God willing to impart? Multiple scriptures give us hints:
"But the path of the just is as the shining light, that shineth more and more unto the perfect day."
"That which is of God is light; and he that receiveth light, and continueth in God, receiveth more light; and that light groweth brighter and brighter until the perfect day."