It seems pretty clear to me that changing one’s body is preferable to changing who you are. The former is something you’re born with, but the latter is something you can decide for yourself.
Suppose, as you do, that your body is not who you are. Then your identity lies solely in your brain. But if that's the case why would disphoria even exist?
If you feel like a man but you don't look like a man, why could that cause any identity problems? It must mean your body is actually part of your identity, so changing it changes who you are
The problem with this argument is that it leads to the conclusion that all change is pointless. If your body is who you are, and you can’t control it, then it’s best just to accept whatever you’re given.
That’s contrary to most of human history, where we specifically try not to take what we’re dealt.
It’s useful to ask yourself: why should vaccines be "allowed" (or "accepted" or "they’re good") but body change shouldn’t be? They’re both as artificial as a Twinkie.