My mother's answer to this whole gender thing is to just categorize people by what private parts they have.
Like...no mom...humans are more complex than that...
Plus that would require actually having to know what private parts people have (because let's face it, you cannot always go off facial features anymore -- if we ever really could) and, personally, that's just not something I want to have to know about everyone I come across.
Plus, okay, then what about nonbinary people? We'd suddenly not get a category at all, accurate or innaccurate -- it just wouldn't exist.
This is why I'm not out to my mother and will never come out to my mother. She doesn't even respect that I don't want my preferred name connected to my biological name -- I can't even imagine the conversation if I tried to tell her I'm nonbinary. Especially since I still have long hair and would kill anyone who tried to change that and I still love long flowy skirts (I like to spin xD).