Sex and gender not the same thing.
Your sex is observed at birth. Whatever you choose to call yourself, if you present unconscious in A&E unless you've had extremely radical surgery the staff will identify in seconds which sex you are, and if your skeleton is dug up a century from now archaologists won't have much issue figuring it out either. A DNA test would demonstrate conclusively. (Including if you're one of the very few rare people with a medical condition affecting your chromosomes, but you would still be male or female.)
Your gender is simply how you choose to express yourself in clothing, hair length, etc etc. It varies widely from place to place and time to time, it is fluid throughout your life based on your preferences. You cannot really have a 'female' gender or a 'male' gender unless you are a believer in stereotypes and believe that long hair/pink/ high heels/ giggling etc = female etc. Why would anyone believe in those stereotypes since they're meaningless and also vary massively between place and time. A century ago the stereotype said pink was for boys.
Your biology is a fixed fact. And your biology is specifically relevant in some situations, usually to do with your sexual organs, ie situations of nudity, medical care, vulnerability to rape etc, necessitating some limited circumstances in which same sex provision is necessary. Your child's biology is usually obvious on a scan long before birth.
Your gender is whatever you want it to be, your child will let you know their preferences and interests in their own time and will probably vary between cat/unicorn/girly stereotypes/ gender neutral / etc etc depending on mood, stage of development, pop culture, fashion, and so on.
What needs getting rid of are restrictive boxes around gender stereotypes most of which is based on toxic masculinity, and a few very noisy people believing that if they identify as something then anyone talking about some part of that group identity they don't personally have then they're entitled to start lobbing their toys out of their pram.