This is untrue. There have been many interpretations by the church fathers, monks, etc. Now most of the public after the roman empire could not read. The only place where they could be taught how to read was in the monastary and so the general public could not read. In any case the manuscripts were written on sheep skin and were well beyond the cost that commoners could afford. Even in the 1600, most could not read.you may not interpret church doctrine, but in the 1600's the reason for the explosion in different christian sub-entities was because of the english translation of the bible- allowing all people to interpret the bible their own way. translations in english may have been done before, but who had access to them and how widely were they published? i'm guessing not very many copies were made and those that were weren't open to the general public. no, it was definately the 1600's translation that was the most important as it allowed the bible to become mainstream as everyone could read them (almost everyone) and printing presses existed to allow the bible to be printed over and over again, becoming widely available.
Think of the most joyful event in your life and then heaven is more joyful then that. There has been a constant source of heresy Donatist, Albigensians, Montanist, Arians, etc.either way, i look back and see a much simpler form of church than todays one, which has to employ complex ideas and forms of thought to keep a hold of people. an example is the way heaven is now perceived. back in the 1500- 1600's heaven was literally behind the clouds, was a place where everyone was warm and was well fed and no-body got hurt. today it is..... actually i don't now what heaven is thought to be these days, but it is not that same simple idea that kept the masses coming back. heaven back then was a better life than the normal life experienced on earth. today (and no-one still bothers to answer my questions about heaven) i don't know what incentive heaven holds to anyone.
http://www.fordham.edu/halsall/sbook2.html#fathers2