Shamanism is different from the main religions of the world because the God of shamanism, the bringer of salvation, is Nature. Not some God-type human.
To honor Nature, we don't need doctrines, a priest, or a monk, or even a shaman to pray for us. We were each born with an inherent connection to the Divine, and Nature is our connection. Please understand that there is a difference between Nature and culture. Humans have always come up with ways to live with Nature. They have had different languages, prayers and gods, and invariably, they end up saying that their way is best way. This, in my mind, is culture. There are, however, truths. Truths that cut through all religious beliefs and cultures. These truths are in Nature.
Once a person opens their mind and heart to the truth that the world around them, Nature, can speak directly to them, then they don't need an interpreter anymore. Religions tend to want people to believe that the figurehead is needed to assure communication, or even worse, that the figurehead is the only one who can communicate. They seem to ignore the fact that each person on the planet is connected to Nature. The point of religion (from the Latin "to tie again") is to support each person in their practice of letting the Nature outside of them talk to, and guide, the Nature inside of them.
Humans have become so self-absorbed that we have forgotten the great power that we live in every day. This power is the power of the Earth and all that grows on her. Nature is what provides for us, not humans.
Any religion that puts the prosperity of their human followers above the well-being of Nature is not in alignment with the Prime Directive. They are part of the problem. Nature and all of it's spirits are what will remain after religions fall away.
What is the Prime Directive?
I have borrowed this term from Star Trek-The Next Generation. In the case of shamanism the Prime Directive is to honor and enhance the plants and animals. We live in the Sixth Extinction, only the sixth time in the eons of time that such large numbers of plants and animals are going extinct. This time, the cause is...US. Humans. Because of this, I feel that the most important thing for any of us to do in our lives is to leave our world better than we found it.