You mistake is thinking that sex is purely about reproduction.
It is purely about reproduction. Humans come in two generic types, male and female, because that's how humans, as a mammalian species, have evolved to create the next generation of humans to perpetuate the species. If humans had evolved to reproduce by budding clones of ourselves from our fingertips, we wouldn't need sexual dimorphism.
Asks the person who is telling literally thousands of highly trained, highly educated doctors and scientists who specialise in this field that they have got it wrong.
No, what posters on this thread have been saying is that, irrespective of the quality of the science, your interpretation of it is wrong.
pediatrics.aappublications.org/content/early/2014/09/02/peds.2013-2958
"METHODS: A total of 55 young transgender adults (22 transwomen and 33 transmen) who had received puberty suppression during adolescence were assessed 3 times: before the start of puberty suppression (mean age, 13.6 years), when cross-sex hormones were introduced (mean age, 16.7 years), and at least 1 year after gender reassignment surgery (mean age, 20.7 years). Psychological functioning (GD, body image, global functioning, depression, anxiety, emotional and behavioral problems) and objective (social and educational/professional functioning) and subjective (quality of life, satisfaction with life and happiness) well-being were investigated."
"RESULTS: After gender reassignment, in young adulthood, the GD was alleviated and psychological functioning had steadily improved. Well-being was similar to or better than same-age young adults from the general population. Improvements in psychological functioning were positively correlated with postsurgical subjective well-being."
No control group, no control treatment. For all we know, a comparable sample of trans young adults would have achieved the same outcome with psychotherapy alone.