On top of that, it's baffling to me that anyone would scream for NPCs or PCs that are classified as "trans" in a fantasy world that's high-magic, because it's a short jump to assume that there would be magic in said world that could flip someone's gender from M-to-F or F-to-M. Hell, D&D had magical items that would do that years ago. Granted, those were usually treated as "cursed" items because they would make the PC's life hell until they could either get new armor and weapons or get the curse removed, but who's to say that a character with dysmorphia wouldn't just hunt down one of those so they could flip permanently? A savvy DM could even make that the nature of a quest for the players if they were so inclined.

As far as PC go, if you're a dude waning to play as a wispy female elf, go for it. Woman that wants to play as a beefy male dwarf berserker? You do you. You can pick your gender from the jump, so be what you want to be. That's the whole point of something fantastic in nature - you make it all up as you go.