I agree, it isnt perfect but young people, their parents and their clinicians have to have the best chance of being the people most likely to get this right - with the very best help and support. I agree that each detransitioner is a tragedy but so is each child denied the pathway that is right for them.
I dont have the wisdom (or the arrogance) to think I can make that choice for others. But I will defend their right to make that choice and fight for them to have the best and most professional help in doing so.
All the evidence shows that around 80% of children who suffer from gender dysphoria before puberty are no longer dysphoric as adults if they are left to complete puberty naturally and not medicated with puberty blockers.
So for every child like you were, Robin, who you believe would benefit from treatment, there are 4 who will be better off if left alone. And until these children are adults we have no way of knowing which group they fall into. There is no diagnostic test which can reliably predict which children will persist and which will desist.
You are advocating for 4 children to be treated with drugs with massive negative side effects (and no benefit to them) in order to help one child who might benefit from them. And even that isn't necessarily true, since you have said yourself: One thing pretty much universal to the trans friends I have - all of whom have known adversity - is a joy in the life they have. So having to wait until adulthood to make this very adult decision has not prevented them from leading happy lives. And the better health they enjoy as a result of not being medicated as children might also mean increased happiness as adults.