"The point is, however, what do 'pronouns' even mean? Do they mean gender or sex? And what is the difference? If we separate them wholly, then how are they not pointless?"
Thank you Robin for your well thought out response. Please forgive the length of my reply.
To answer this question, pronouns are used in society to refer to noun, often with a gender attached to it, not biological sex.
For example, A friend of mine is technically intersex, but she has been raised as a woman, dresses like a woman, and identifies as a woman. Should she have her own set of pronouns because she is intersex? No. Society sees her as a woman, she sees herself as a woman, she uses she/her pronouns. That's a culture thing, a gender identity, not a biological term. Biologically, she's not entirely exactly female.
Pronouns are used socially, they are how we talk to each other and refer to each other. They are part of the social construct of gender. Which is how people are, how people act, and how society views them. Male and female, are biological terms, around sex, which is something more medical. Sex is a biological science fact, Gender, is more of a social construct. A very important social construct. Social constructs are not biological constructs. I am a woman, biologically female. It can be very hard for cis people to understand the difference between gender and sex, because for us it's always been the same. It takes someone, namely a tran person, who has a different gender than biological sex, to realize they aren't the same thing. It's kind of like, if a person eats potatoes for dinner, and then potatoes for desert, they think dinner and desert are the same thing. Desert just feels like extra long dinner. However, if another person eats potatoes for dinner, and ice cream for desert, then they start realizing they aren't the exact same thing. I suggest you consider reading about the difference between gender (a social construct), biological sex, and gender identity. Understanding the differences are key here.
Since you seem to be writing about this as a christian, I would like to offer my own perspective I developed around trans people back when I was a christian. As a child, I read the entire bible multiple times (I was quite devout). I learned to accept trans people when I was still a devoted Christian and I can tell my argument for it.
What happened, was I had a really good close friend who was/is still a good person. After being close to them for a year, they attempted suicide, much to everyone's shock. After they got out of the hospital and healed, we talked a lot. And I learned the reason why they were having such a hard time was they were trans. They hadn't transitioned, but wanted to, but understandably afraid of the social reprucsions (this was 2006). The next 5 years was really rough. They attempted suicide 3 more times, and engaged in a lot of self destructive behavior. I honestly thought they were going to die. Then eventually they came out as trans, transitioned, and since then have been way better. This is a good person, who is kind, and spends their free time volunteering with meals on wheels, bringing food to elderly people. Honestly if they hadn't transitioned, they would be dead.
It can be easier to be against an ideology, when you don't see the actual people who are hurt without it, and how the whole society hurt.
I've met many other trans people, who plain out tell me they would be dead if they hadn't transitioned. I'm pretty sure, 20 years ago, there were less trans people because mostly they were just rejected until they committed suicide. When society as a whole says a person shouldn't exist, that they make no sense, that their identity isn't allowed, people who are that identity, there isn't space for them, and they eventually disappear.
For me, it was more, do we accept a different ideology about gender? Clearly there must be a difference between sex and gender and the very existence of trans people indicates something is happening. But I then when to a bigger question. What would make the world a better place? For me I looked for guidance in the Matthew 7:15-20. Beware of false prophets, who come to you in sheep’s clothing, but inwardly they are ravenous wolves. 16 You will know them by their fruits. Do men gather grapes from thornbushes or figs from thistles? 17 Even so, every good tree bears good fruit, but a bad tree bears bad fruit.18 A good tree cannot bear bad fruit, nor can a bad tree bear good fruit. 19 Every tree that does not bear good fruit is cut down and thrown into the fire. 20 Therefore by their fruits you will know them.
Was trans gender ideology false, or a good fruit tree? I really couldn't tell. Whoever a totally new thing enters my world, I use this test. What is the fruit?
Be being allowed to transition, my friend was able to stay alive. They are a very good, kind person, who brings food to elderly people, without them, the world would be less good. They add a lot. My nephew is trans, they are also a good person, very loving and good. If they were dead, the world would be a less of a good place. Looking at the actual people in my life who were trans, I felt the world benfited from them being alive, and not killing themselves. The ultimate test for me, accepting trans as a valid identity, lead to more good people being alive, it brought good fruit. People can argue all day and night about the intellect or definitions, etc. But if ultimately the world is a better place, and it is, then it's not a wolf, it's a good fruit tree.
Ultimately I don't think I'm capable of understand everything about gender, so for me it's not a question of if it's right or wrong. I have found the world is a better place when we accept trans as a valid identity. It bears good fruit, because fewer people are killing themselves, and that's to me what Jesus said is the true test. The scribes and others in the gospel are the ones constantly arguing and using their intellect against Jesus with their knowledge, which is fine. But maybe the real test is looking at the fruit. Seeing if something good comes from it. Accepting trans people is the good fruit tree, and that's enough for me.