It's true that there have been many wise men/women with well considered philosophies and opinions. Consider my sig line and it's well known author. I consider it a perfect description of our relationship with Jehovah, a consideration not shared in any measure by my friend Frank.
So, regardless of erudition or razor sharp insight, when we look at things not in the canon, we risk hopeless confusion as we try to discern God's message. For the Bible was inspired and written, not as a scientific treatise, but as an explanation for the least sophisticated of us to understand how misery and death came into our world and what God intends to do about it.
For that purpose, the canonical scriptures are sufficient and we do well to consider the words of the apostle John regarding God's injuncture regarding additions and subtractions from 'scripture' - Revelation 22:18,19
However, I understand other belief systems have their own 'scripture'.