One other important point I should mention is that in the psilocybin studies in progress, they are treating existential anxiety that is reactive to a cancer diagnosis. Participants who have a history of anxiety or panic disorders are not eligible to enroll for some of the reasons you mentioned.
I agree that cannabis may be a more effective alternative for some individuals who are prone to anxiety. Recreational/personal psilocybin use has been known to trigger anxiety problems in vulnerable individuals, especially when proper care has not been put into set (mental/emotional preparedness) and setting (environment/support).
Just to be clear, I am not advocating recreational use of any illicit substances!