That sex is binary makes sexism so easy. What if sex existed on a spectrum?
But, you may reply, it doesn’t. Contrary to so many transactivists, sex is a matter of biology, and you are either male or female; barring the exceptional, one has either XY chromosomes or XX chromosomes.
True, but saying that sex is physiological rather than emotional, an objective reality rather than a subjective feeling, need not imply that it’s binary.  Imagine a spectrum: people with XX chromosomes and functioning female reproductive anatomy at one end (implying a certain level of estrogen); people with XY chromosomes and functioning male reproductive anatomy at the other end (implying a certain level of testosterone); in between, pre-puberty people (neither completely female nor completely male yet, post-menopausal people (no longer completely female), people with hormone variations from the norm (due to natural levels or injections), people with surgical variations (for medical reasons or cosmetic reasons—we may want to distinguish between the two), and so on. There could be multiple (physical) determinants of sex, and people would be more or less male or female depending on their particular constellation of chromosomes, hormones, and anatomical bits.
In many ways, such a world would surely be more complicated. For instance, competitive sports would have to be completely reorganized not according to sex, but according to height, weight, muscle mass, etc. But surely, it would be, eventually, manageable.
Another way to reduce sexism would be to adopt sex-neutral language, because if you didn’t know whether the person was male or female, you couldn’t discriminate on that basis. This would involve the adoption of sex-neutral names and sex-neutral pronouns  and the elimination of ‘man’ and ‘woman’ (as in ‘police officer’ instead of ‘policeman’). We would retain ‘male’ and ‘female’, of course, but mentioning sex would be relevant only in biological/medical contexts (and personal contexts regarding sexual interaction); to use ‘male’ and ‘female’ in everyday discourse would seem, as it does now, rude.
 Nor need it imply essentialism in the sense that physiological sex is essential to one’s identity (for example, although I am female, but I have never referred to myself as a woman because as far as I’m concerned, my sex doesn’t define me except in medical contexts; it does imply essentialism in the sense that physiology is essential to one’s sex.
 In many cases, given the spectrum mentioned above and the hoped-for elimination of gender, it might not even be possible to know whether the person was male or female if you actually saw them.
 Though, please, not ‘they’ because of the consequent singular/plural confusion; there’s no reason we can’t introduce three new words, such as ze, zim, and zer.