Ayahuasca is used as a purgative by traditional folks- its a dewormer, so they had good reason to do this. I'd suggest the physically medicinal side of ayahuasca brew has been mistakenly linked to its other use.....
I would like to have a true shamanic experience, but I don't know what that means, and I can't see why I have to go to the amazon to do it. If i did it, my scepticism would likely lead me to difficulty. I don't like how western psychedlic users revere old religions (well, how old are they?) and shamanism as this absolut pinnacle of thought.... Most shamans would freely admit they have no idea how they are doing they are doing, they may suggest they are communicating with ancestrors because these plants are ancient, but thats just an educated guess on their behalf.
What is a shaman? In everything I've read, I still can't define it. If its ritual, I'd call it stagnant, because rituals are unchanging due to doubt and mistrust of further, different examination. I don't think the context for DMT should be old and ingrained, though that could help to ground one. DMT is very spontaneous which is why I don't tend to use it with other people who almost tie me down through social etiquette and demands.