Maybe there are fair ways to regulate people who transitioned prior to puberty. I have no idea how you can even define what's fair for people like Lia Thomas who transition in their 20s.
I find the notion preposterous that a male athlete would go through puberty and then transition (hormone therapy, gender reassignment potentially) as a ruse, solely to gain a competitive advantage against lesser competition. There are a ton of female athletes who are physically and genetically gifted that could absolutely whip my ass in any physical competition, including a fist fight. Is it fair that they have those physical and genetic advantages that other female athletes don't? Should they be penalized because of it?
Look at the shoulders on this broad:
I think the discussion (the legitimate one, not those being had in random pockets of the internet) is coalescing around requiring that certain hormone levels (e.g., testosterone) fall within certain ranges. In athletics, you can never guarantee physical parity (Britney Griner can dunk a basketball; I can't), but you can attempt to ensure that no athlete has an unfair chemical advantage. There's obviously a lot to think through. What if a female athlete (assigned F at birth) just naturally produces more testosterone than other women, for example? Would we have to require her to undergo hormone therapy to get within the same acceptable range for trans athletes? Or would those ranges only apply to trans athletes?
At the end of the day, what we, as laypersons, can and should be doing now is not attacking the trans athletes themselves who are merely trying to navigate a complicated and evolving system. (I am NOT implying you are doing so, to be clear.) Instead, we should focus on developing rules and systems that are as fair as possible. Everybody deserves dignity.