But having just one sports category for both sexes together automatically means all sports will end up male only, or almost entirely male, with a handful of exceptional female athletes sprinkled in here and there.
I disagree that "categories based on sex" in sports - and some other areas of life such as locker rooms, toilets and health care - are "outdated, unnecessary and, by definition, sexist."
Female and male humans are physically different in myriad ways due to the fact that evolution has arranged for each of the two sexes to play markedly different roles in reproduction and perpetuation of our species.
Females can accomplish some truly amazing physical feats that males can't - get pregnant, gestate a new human being to the stage of viability, go through labor, give birth, keep babies alive, thriving and provide them with immunity simply by breastfeeding.
But because our bodies are built to shoulder the lion's share of the physical burdens of human reproduction, women and girls have a host of physical features compared to boys and men that mean we don't and can't perform as well in most sports as boys and men.
After all, nearly all sports were originally invented and designed by men for the explicit purpose of showcasing and highlighting the kinds of physical feats that male bodies, and male bodies alone, are built for and particularly good at. So no wonder boys and men outperform girls and women in sports by rates that in athletes 18 and up range from 10-12% to more than 60% - and in some specific physical tasks like throwing a punch, a ball, discus or javelin - by more than 160%.
The physical features that girls and women have which make it unfair - and unsafe - for us to have to play and compete in sports against boys and men include much smaller hearts and lungs even when height and weight are the same; lower CV capacity and lower hemoglobin; wider pelvis and hips, and thus more of Q angle, making for less efficient running and kicking; far less lean muscle mass, upper and lower body strength; bones that considerably less strong and sturdy; greater susceptibility to lower limb injuries and head and neck injuries, including concussion and whiplash; considerably less grip strength, arm strength, explosiveness and ability to jump high... and so on.
Of course, there is a place for mixed-sex sports like tennis doubles, volleyball, tag or flag football, mixed running and swimming relays. But mixed-sex competitive and recreational team sports are usually played under special rules to make them fair and safe for the female participants.
Plus, in our peak athletic years girls and women spend one week out of four menstruating, which can be very painful, and another week in the often physically uncomfortable or downwright difficult premenstrual phase. Moreover, many girls and women have various forms of gynecological issues - and female athletes who are sexually active with males all have to worry about, and deal with, pregnancy and contraception. In adulthood, most female athletes have their ability to participate in sports on par with males further diminished by pregnancy, childbirth, maternity, breastfeeding. And starting in our 40s, women have to deal with the enormous physical disadvantages caused by the yearslong process of peri-menopause and menopause.
So anyways, I disagree that "categories based on sex" in sports - and some other areas of life such as locker rooms, toilets and health care - are "outdated, unnecessary and, by definition, sexist." The complex "higher" organisms on our planet have been reproducing sexually for millions/billions of years, and sex and physical sex differences have always been at the heart of most animal, plant, mammalian, primate and human life.
I believe sexism, sex stereotyping, and rigid sex roles and expectations are outdated and unnecessary - and I'd like to seem them become things of the past. Which is why I am against the gender identity movement, which seeks to promote, reinforce and enshrine sexist stereotypes and make those stereotypes the basis for categorizing people and organizing society.
But human sex itself and all the physical differences that make the bodies of male and female humans totally dissimilar to one another in innumerable ways are not going anywhere. They are here to stay.
In fact, the research on human sex differences that's been done over the past 30 or so years using sophisticated methods to study human cells, genes, tissues, organs and body systems show that there are many, many more physical differences between male and female humans than many in medicine, science and the general public previously assumed.
As for your claim that a separate category of sports for females is sexist: the dictionary I use, Oxford defines sexism as "characterized by or showing prejudice, stereotyping, or discrimination, typically against women, on the basis of sex." Many would find your view that women and girls shouldn't have our own separate sports category to be sexist, not my view that we should. Because your view if put into practice would mean that the vast majority of girls and women would be excluded from sports entirely right off the bat - and it would mean no female athlete would ever get a chance at winning a podium place, obtaining a sports scholarship, receiving awards for excellence and achievement, obtaining a sports endorsement deal, sponsorship or getting a job in coaching, sports administration, refereeing, or working as a media sports commentator or journalist.