The World Health Organisation, for example, talks of the need to depathologise trans health: "trans-related and gender diverse identities are not conditions of mental ill health, and classifying them as such can cause enormous stigma" and goes on to add that "Inclusion of gender incongruence in the ICD should ensure transgender people’s access to gender-affirming health care."
I think this is the central problem - there isn't agreement on what is being treated.
The WHO paragraph above only makes sense if you follow the 'born in the wrong body' narrative - if there is nothing wrong with the brain there must be something wrong with the body. In turn 'wrong body' only makes sense if either you believe in a gendered soul, or you believe that particular traits can only belong to a male or a female - the choice is religion or sexism.
Any other explanations e.g. gender dysphoria that might have been triggered by a variety of causes, and that might not be permanent, must be rejected if you have to reject a mental health diagnosis. In a society where schools have been told that gender must be affirmed, how does a doctor talk about other factors like mental health, autism and trauma?
It seems odd in 2020 that stigma should be a reason to deny the existence of a mental health link, but here we are. I think the only conclusion can be that sometimes it is good to be an outlier. However, its not difficult to see why GIDS is in a mess. Who needs Mermaids to apply pressure when the BBC and Netflix are happy to tell children that football is for boys, girls don't wear blue, and a doctor can give you a new body?