Singular they is over 600 years old by the way: https://www.oed.com/discover/a-brief-history-of-singular-they/?tl=true

As a trans person, my gender dysphoria is not something caused entirely by social gender roles. Medical transition has greatly alleviated the majority of it. Anecdotally, within the first week of hormone therapy, my dysphoria improved dramatically while only being out of the closet to 2 people outside of my therapist and the medical professionals who prescribed my hormones. It has continued to improve, although I'm still waiting for the surgery that will resolve the remaining things that hormones can't fix.

Also, there are studies around brain structure differences between men and women, and transgender people tended to have brain structures in line with their gender, not their assigned sex at birth: https://en.m.wikipedia.org/wiki/Causes_of_gender_incongruence#Brain_structure

Perhaps you should believe people when they tell you who they are, and get past your discomfort drawing arbitrary lines in grammar regarding pronouns, when singular they predates the fall of the Byzantine Empire by 75 years.