I don't believe that shamanism without hallucinogens is authentic shamanism or comfortable shamanism.
For unknown reasons, there is a tremendous concentration of psychoactive plants on the South American continent. The South American continent has more known hallucinogens than the rest of the planet combined.
I'm proposing on one level that hallucinogens be thought of as almost as social pheromones that regulate the rate at which language develops, and therefore regulate human culture generally.
In the absence of good scientific data about the effects of artificial hallucinogens it's good to stick to the natural ones.