This results in zero women playing sports.

I wish so much that the top women athletes were above the replacement level. It would create so much interest, we could all root for these women. It would be a benefit in terms of equal rights arguments when you could point to a woman being better at a sport than the men.

But unfortunately that's just not reality. Male replacement level players are better than the best of the best female players. Having women on a team means having a player that's below replacement level on the team. Meaning they could find a male player from a minor league team that could play better. This will never be a winning strategy.

There isn't really a rule that prevents women from competing at the top level in professional sports at the top level. There just isn't any women that can compete at that level. I remember around 20 years ago there was a woman goaltender that was really good and there were hopes she might be good enough to play in the NHL. Ended up not being as good as the male goalies in the minor leagues, so didn't make the cut to get to the NHL.

It's just one of those things where reality doesn't conform to what we want it to be from a political standpoint. Women's leagues exist (and should continue to exist) because if they didn't women wouldn't get to play sports. There's always thousands of men that are stronger and faster than the strongest and fastest woman. It sucks, but it's how it is.

People watch the NBA over the WNBA because they want to be the very best at the sport. It's not a segregation rule that prevents women from playing in the NBA, it's just that there aren't any women that make the cut. Same goes for most sports.

But in the end it isn't really a requirement to be the best at a sport to deserve equal rights. Sports are sports and it's not really that important that there aren't any women that make the cut at the top level of play. There's more important things to worry about.