She's not being banned from participating. She just has to prove she has the testosterone levels of a cisgendered woman, and if she doesn't, she must get the level lowered. According to the ruling, if a woman has above a certain level of testosterone in her blood, the level must be lowered before she can compete. Seeing how testosterone levels are what causes secondary sex characteristics in men, and also the main reason why men are much stronger than women, this makes complete sense to me.
The ruling's press release claims:
No female would have serum levels of natural testosterone at 5 nmol/L or above unless they have DSD or a tumour.
Assuming this is accurate, and a woman has testosterone levels above 5 nmol/L due to one of these reasons, AND it gives a significant advantage, having the athlete take a pill to be eligible in competitions seems okay to me.
I mean, when someone takes steroids, they're literally just injecting testosterone into their blood. If a woman has some medical condition that make her testosterone many times higher than normal, it's a pretty significant advantage. Like, arguably as much as taking steroids.