I'm fine with new genders. But while everyone likes to say that gender is a social construct, they tend to parrot the line without actually considering its meaning.
Yes, gender is a social construct. But that's exactly the thing - it's socially constructed! Genders as social constructs are made by the combined social interactions and negotiations of thousands if not millions of people. If you just sit down by yourself and try to invent a new gender to describe yourself, that's not a gender. That's just a nickname. Social constructs can only be made socially. That's the entire point of a social construct - a bunch of people getting together and coming up with some new label to describe some aspect of the word. Without that social element, you're just writing fanfiction. It's like that wiki of thousands of genders that was recently deleted. In truth, almost none of them were true genders, as they were almost all just created by individual teenagers acting alone.