I think the essence of simplicity that is conveyed by the phrase works, but, I agree, it is too simple. How do you sum up the internal struggles, expectations and culture into just a few words? I have a male, XY body, which I have had from birth. My mind/spirit is female. Somehow, there is a disconnect between the body and mind/spirit which creates horrible feelings of anxiety and depression. I tried to play the part that the outward appearance conveyed. Internally, I struggled the whole time. It took me 25 years to finally realize what was going on between me and my body. Once I finally accepted who I was, I was and am able to do something about it.
What irritates me most about the phrase is the immediate write-off that happens after someone says it or hears it. Something like, "oh it's just that simple, right?" No, it isn't that simple. You have to account for relationships, education, habits, feelings, emotions and everything in between that makes us who we are. As others have said, I would not wish this on my worst enemy.