Shamanism exists with or without ritual, and with or without religion. One does not require nor preclude the other. It is certainly possible for a very religious person to have a shamanic calling, just as it is possible for a very great shaman to be without religion in an organized sense. Though it is obvious that every shaman has religion in it true meaning as a linking back, as in 'of all time. The ritual comes with the religion and shamanism is no religion.
Shamanism exists with or without ritual, and with or without religion.
One does not require nor preclude the other. It is certainly possible for a very religious person to have a shamanic calling, just as it is possible for a very great shaman to be without religion in an organized sense.