I got a sense of the concept of Original Sin sometime during the period when I was becoming a believer, back in the 80s, and far from Coyote's take on it for me it was like a brilliant light went on that illuminated this dark world. I felt that finally I had an explanation for the evils in this world that otherwise have no explanation. To my mind the doctrine is essential and precious for that reason. It takes a chaotic world in which people do horrible things to each other and makes it understandable.
Unlike you, I do not consider myself or my species to have been born evil, nor do I consider that we require the intercession of a shaman to cure this inherent (but nonexistent) evilness.
But I can see why shamans would want to promote this doctrine, as it empowers them and puts grits on the table.
"Do what I say or you'll be forever damned. But for a small fee..."
Bah!
Religious belief does not constitute scientific evidence, nor does it convey scientific knowledge.
Belief gets in the way of learning--Robert A. Heinlein
How can I possibly put a new idea into your heads, if I do not first remove your delusions?--Robert A. Heinlein
It's not what we don't know that hurts, it's what we know that ain't so--Will Rogers