i'm tired of pretending it's not

The most credentialed medical bodies disagree with you

Um, actually, gender dysphoria IS a mental disorder.

Now, transgenderism is a perfectly acceptable coping mechanism for that disorder for most circumstances.

The meme says transgenderism is a mental disorder which is still inaccurate.
Gender dysphoria is a mental disorder and is in the DSM-5, partly so diagnostic criteria exists and for gender-affirming care to be available.
Also, not every trans person experiences gender dysphoria.

If one does not have gender dysphoria, there is no real reason to be transgender. If living as your biologically defined gender doesnt cause you distress, but you choose to change it anyway, at that point it's just a fashion choice. And I know that is happening, and that's a big part of why it's so controversial. We don't want minors getting medical intervention to support their fashion choices.