I've been lurking for a while and this interesting, civil, discussion has helped me to solidify my thoughts on gender a bit, to the point I feel I can tentatively share them...
My current thinking is that gender might be a real thing and has limited use on a population level, but also that it is no more important for determining if you as an individual are male or female than your height is.
If you'll bear with me, I'll try to explain...
If you take 200 toddlers, half of them male, half female (sex not gender), and put them in a room containing cars and dolls, you might observe that on average, the males spend more of their time with the cars than the dolls and vice versa. However, if you take two individuals out, one male, one female, although it is more likely the male will prefer the car and the female the doll, you cannot be certain.
I think it is like this with many "masculine" and "feminine" stereotypes - they are based on what happens at a population level on average and not on an individual level.
I also think that there are 'true' stereotypes that are to do with our nature/biology and 'false' stereotypes that are to do with nurture /society and can be harmful. For example, the idea that men are less risk-averse than women may well be down to nature. The idea that women wear lipstick is down to society. But neither defines an individual as belonging to the population.
I think of it as overlapped population bell curves, to illustrate. And this even produces a sort of gender "spectrum" idea.
My issue with trans ideology is that it seems to draw a line down the middle and say one side should be 'men', one side should be 'women' (thus losing the original definitions of those terms).
The other trouble is, I can do this with height as well! Take the heights of 200 men and women (biological that is - I wish I didn't need to state that!), the men's average will be taller than the women's. But take one of each from the groups, and although it is more likely that the man will be the taller, it's not guaranteed.
On an individual level, height tells you nothing about their sex. And sex tells you nothing about their height. Only about probability. They're related, but they're not.
I wouldn't want to put a line on the bell curves and say "everyone over 5'7" can be a man, everyone below can be a woman". So why say "everyone who presents as masculine can be a man and everyone who presents as feminine can be a woman", as trans ideology seems to be doing with gender?
Worse still, it's now come down to 'feels like'. So this to me is the equivalent of saying if you 'feel' you're 6'3" you can be in the man category... even if you're actually 5'2" and have XX chromosomes...??! That's where it loses me altogether.
So, although I think gender exists in a way and is possibly relevant as a concept to describe population scale differences between men and women, (job preferences, for example), on an individual level it's completely irrelevant to what you are and what facilities/services you should use. That's down to your sex.