A trained therapist (the definition of which will have to wait) is crucial when you leave the domain of surface psychological work, which can last many years even at above high doses without a correct structure in place and understanding of the phases of psychedelic work (there are two phases: sense tuning, where 99% of journeys end because of lack of attention control and reactive immersion of the attention in sense perception changes such as visual or auditory hallucination which then become full experiences due to the immersion; and the work phase, where you coordinate with the psychedelic on the unfolding of your intent).
Once you begin work on root causes of the psychological structure a seasoned psychonaut may not be sufficient, unless they have themselves done root work, because if seasoned means years of experience at high doses at the surface of the structure, they don't have the capacity to hold you and at the same time allow you to continue through root work, when your points of reference framework is taken apart temporarily for the purpose of understanding the pattern of self-judgement that is ingrained in the foundation of your perception of reality, and during that short period of time when your points of reference are suspended, everything within your present environment including empty space reveals a memory that is connected to self-judgement and which triggers self-judgement in the moment. This is happening while the psychedelic is digging out the root of that pattern and until it is dug out, your inner and outer perception becomes a unified experience of self-judgement. Until the root is uncovered, and prior to that day of therapy, the experience of self-judgement in daily life was a series of disconnected nodes in an invisible graph. Depending on your involvement in self contemplation, some patterns within the graph may have become known to you, but that didn't stop the experience of recreating situations that further the self-judgement. Once the root is uncovered in therapy, the whole graph becomes available to your conscious mind and you are able to clearly see the initial experience or set of experiences from which the self-judgement pattern evolved, and are at the same time able to understand every single past experience that had the mildest expression of that pattern and see the aspect of your personal identity that is the growth of those experiences. Most importantly, from that moment onwards integration becomes possible, integration being the recognition of the pattern in the present situation and connection of the present situation to the root of the pattern which enables you to introduce conscious response into what previously was habitual reaction, thus transforming the pattern. Apologies for going off track but it seemed useful to share.

The hell that a therapist has to do with it is the one you are experiencing in the moments just before the root gets uncovered, which hell may seem to last an eternity as the uncountable previous experiences of self-judgement become condensed into the space of now, and not just the experiences, but the very part of your personal identity to which in a way you are fully attached and without which you would feel loss, even though you consider it a pattern that introduces chaos into your daily experience. A good therapist, even one without extensive personal root cause psychedelic experience, will be able to help you navigate that hell, and reach the root. Without the proper structure and guidance you might not reach that experience of even beginning the work on the root, and if you do, a different outcome could be that you do not uncover the root, remain with the memory of a bad trip in which "I got stuck in a loop of self-judgement that seemed to never end", and are potentially further away from coming back to that subject and finishing the work by burying the root due to this experience, because if I went through that and didn't finish it in that sitting, I am for sure gonna take a nice long break from trying to understand self-judgement, and the condensed experience that would have led to uncovering the root will have had at least some temporary impact on my sensitivity, so I'll be fine dealing with self-judgement for a while.

I completely understand your worry though, and have one of my own, because it seems to me very possible that a future awaits where the structure of psychedelic work is not known, and the work will be limited to the surface, curing depression, learning incredible skills, and not realise the possibilities for the deep work. My worry is that psychedelics will be productised before their depth capacity is fully understood, and the product will be so appealing, near limitless in application and well marketed, that the depth work will have to wait for the next disruption opportunity in the product cycle, which in this market seems to be counted in the thousands of years.