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.