Twinkies don't taste as good as they used to.
Diagrams are unnecessary because Jesus never needed them to explain anything to the common person who wasn't a scholar or a philosopher. Paul himself stated that his advanced understanding of things was unnecessary.
It's very possible that the Trinity is correct when you deal in purely spirit concepts (what shape or form is the mind, essence, love, intention or hope?), of which we understand even less than purely physical ones. But there is no indication in the scriptures that if one accepts Jesus as the Son of God you will lose your salvation.
15 “But what about you?” he asked. “Who do you say I am?”
16 Simon Peter answered, “You are the Messiah, the Son of the living God.”
17 Jesus replied, “Blessed are you, Simon son of Jonah, for this was not revealed to you by flesh and blood, but by my Father in heaven.
Peter's answer was sufficient for salvation.