The Bible disagrees with you...
[KJV] Acts 8:26 And the angel of the Lord spake unto Philip, saying, Arise, and go toward the south unto the way that goeth down from Jerusalem unto Gaza, which is desert. 27 And he arose and went: and, behold, a man of Ethiopia, an eunuch of great authority under Candace queen of the Ethiopians, who had the charge of all her treasure, and had come to Jerusalem for to worship, 28 was returning, and sitting in his chariot read Esaias the prophet. 29 Then the Spirit said unto Philip, Go near, and join thyself to this chariot. 30 And Philip ran thither to him, and heard him read the prophet Esaias, and said, Understandest thou what thou readest? 31 And he said, How can I, except some man should guide me? And he desired Philip that he would come up and sit with him.
Does it? Did you ever ask yourself why the eunuch was reading the Scriptures then? If he believed he needed a man to understand them, then why was he reading them?
You have missed the point of the passage, namely, that this portion of scripture is harder than others, and he was asking the correct questions from the text ... "of whom does the prophet speak?"
Also, do you use this passage to support a doctrine that we as individuals cannot understand the text without a priest, church, etc? What about all the commands in scripture that we are to read, memorize, teach, preach, obey, etc. the scriptures? Does that not imply it is understandable?
I'm not convinced that what you espouse is taught in this passage.