I would argue that there are 2 sexes and a few relatively rare abnormalities.
Just like humans are fundamentally bipedal, even though there are some birth defects that cause people to be born without 2 working legs.
Real intersex babies are born about 1 in 2500. Rare? Yes, still a decent number.
This does not at all mean that I am on board at all with the LGBTQ3Plkjmnbdtherfhe people.