I'm not into competitive sports, but I don't think they're fine. I'm in favor of gender neutral or weight classed leagues.
On some level though I think it's okay to tell trans athletes they can't compete in certain leagues. I'm colourblind and I can never be a firefighter or a pilot or a cop, and I had to back off from my dream of doing art school because I didn't think I could compete. There are biological restrictions which preclude things we want, and I do think being trans precludes competing in the sex based leagues, but as mentioned earlier we can revise our leagues to make them a better fit on a per sport basis.