So, I fully support trans people competing with cisgender people in sport. I also think there's loads of sports where you could gender desegregate it - basically all the sports that don't rely on strength and size.
So I said that bit, but then I also said that if you desegregated sports like swimming, football, rugby, etc etc, then you would never see a woman in a top team or on the podium at the Olympics ever again. Is that not factual? Even Ledecky, who is a ridiculously good swimmer, would not even make the men's swimming final at the Olympics.
I think you could desegregate sports at lower levels too - I've seen it done and experienced it. I was in a middle tier team in cricket with a bunch of dinguses, and the sometimes Women's A Team players would join our matches. They were as capable or better than the blokes most of the time. However, these women went on to play internationally, on TV, picking up contracts and stuff by playing against other women. If it was desegregated she'd be playing with shmucks like me who never even really liked cricket.
Am I wrong?
It's a pretty simple issue when you think about it. Men aren't magically more capable than women, there are a variety of things that men are more likely to have which make them, on average, more capable than women at certain tasks. So, isolate those particular traits and segregate by them. If height is the biggest factor in a certain sport, for example, then, sure, segregating by sex will get you one side that is generally shorter and one side that is generally taller, but segregating directly by height is a far more logical and simple approach.