The Bible is said to be God's revelation to mankind. It supposedly contains a vitally important message from God to each and every human being. Of course, the Bible as we know it did not even exist until three or four centuries after Christ, so a good portion of humanity never had any opportunity to enjoy its revelation. This fact is further emphasized by the Bible itself, when it notes the mysteries of God which were previously hidden (Ephesians 3).
The revelation contained within the Bible was obviously a progressive one and was further limited by the narrow scope of its distribution. No one seems to assume that the Old Testament portion of the scriptures was available to any but the Israelites. Whatever purpose it served in preparing for the eventual unveiling of the final mysteries, that purpose did not include most of humanity.
Revelation is really just another word for communication. As noted before, real, effective communications must take place in the mind of the recipient, not in that of the communicator. This is the basic problem with many attempts to communicate. The message seems clear to the messenger but becomes lost to the hearer. For revelation to actually take place requires more than a valid message. The revelation must be distributed and must effect proper understanding. Of course, in the case of the Bible, that is where the church claims its necessary role in God's revelation. They preach and interpret the Word.
The disconnect in this story surrounds the issue of universality. Supposedly God's revelation is aimed at all humanity, at least since Christ. In other words, it was God's intention, post Christ, that each and every human being should hear and respond to His revelation. Since the Bible, which represented that revelation, was not available to everyone by God's direct actions, a mechanism for universal dissemination had to exist. Thus the role of the church.
However, no one I know would suggest that the church's efforts at spreading the message of God's revelation has been more than minimally successful in terms of all humanity. Even within western civilization, where Christian doctrine has molded societal thinking, the churches constantly bemoan their lack of success in making the message effective.
The church contends, generally, that God has done all He needs to do to hold mankind accountable for rejecting His revelation. Thus, in some pending future judgment, God will rightfully condemn each and every one who has not listened to what the Bible says and responded correctly. By this contention, the church claims that God's revelatory process was complete at some point in the past when He could justifiably say that He had done all He could or would do to make His Will known. This line of reasoning never addresses the question of when the revelation process was actually complete or how it could possibly apply to those who never receive it, for whatever reason. This supposed process is further compromised by the very fact noted above- until someone actually understands the message, no revelation has actually occurred. Simply dropping a completed book, whenever that actually occurred, somewhere on the earth does not by itself reveal anything, much less universally.
A universal divine revelation seemingly would involve a less haphazard process. In fact, the Bible deals with that very issue (Hebrews 8: 7-13). This passage addresses what would logically be necessary if God's plan involves a universal revelation, the kind the church contends is contained within the Bible alone. The revelation described in Hebrews 8 is surefire, not at all like the church taught version. The message goes unfiltered from the mind of God to the understanding of every man. Until that happens there is no divine revelation, just words on a page.