I think that similiarities between sz or psychosis and shamanism are highly over characterized. A shaman is a healer, knows about plants and their healing properties, a psychotic person can have that knowledge but that alone doesn’t make one a shaman.
About mysticism, is trully a matter of perspective. Some szs believe in their delusions, others eventually don’t. While psychotic most of us believe in our delusions, hence the need for medication, and they’re often of a spiritual nature and/or paranormal. The deep end of the current belief systems that our era provides is, at best, an attempt to make sense out of the world that provides some kind of confort to our need to catalog and name everything.
I also think that a person who believes in a single truth about what life is is thinking in a delusional way because there actually is no answer. The ones humans can make up will always be human answers but there are more consciousnesses more out there than our own.
That is why philosophy is so important, and that is why science is so important, and that is also why some people find the spiritual path of life so important to them.
From my perspective, I don’t think its spiritual when I contemplate the nature of reality and it gives me tranquility like a divine touch. I think that is fairly normal, or should be, that one contemplates the nature of reality.
I don’t remember who said it but “To entertain a thought without accepting it is a sign of an educated mind” or something like that