Did I say that? I'm thinking not.
So is skin colour and religion. Just because you can categorise something doesn't mean you should divide people in that way. Usually when you do it you do it to advantage and showcase people and not exclude them. However, I'm not advocating for or against inclusion of transgender people in elite sport as there is an obvious issue with transgender women having a physical advantage in many/most cases.
Only to you but life is more nuanced than that. The fact that the world is struggling with the issue suggests that it isn't that simple. Nobody seems to have an issue with transgender men competing in elite male competition for example. So we are really talking about only creating a separate competition for transgender women to compete against each other. Given that this is in effect a ban it has to considered and deliberated upon as you are formalising discrimination in a couple of ways and if you have to do this you want to be very certain it is the best, or least shit, option. Or if you go down the regulating testosterone level route it strikes me that mandating such an intervention for non-medical reasons has significant ethical issues attached.
I can see both perspectives as I have a son playing elite sport and a transgender nephew, and it is a hard life especially as you transition and given that being recognised as the gender you are (not the sex) is a major step in healing the damage your gender dysphoria the world treating all transgender women as other in the way you suggest is harmful to all, and not just the odd person prevented from competing. It could be argued that the wellbeing of transgender women is more important than mere sport. I wouldn't argue this as I don't think sport is "mere" anything and at the elite level the time, effort and dedication is not only admirable but something we need to retain the integrity of. My son plays his sport at a fairly elite level.
If he transitioned he would be easily the best female player in the world, by a significant margin. Such whataboutisms are however dangerous if that is all you consider.
As I have said repeatedly I don't know (or see) an easy solution and it may well be that the least shit option is not allowing transgender women to compete at the elite level. But I think the issue deserves more discussions and debate than "Its obviously a bloke".
And there is also far more to sport than the elite level. This is an interesting read.
https://www.insidehook.com/article/sports/trans-athletes-win-boys-sports