is there some similar text for neopronouns?

I’m unfortunately not aware of any in particular, since my personal field of knowledge around the general subject hasn’t been terribly focused on neopronouns specifically.

f I lived in a world where the only pronouns were he/him then I doubt I would ever think to use they/them.

I can understand that, but do remember that this is the exact world that people who now go by she/her pronouns lived in, and they didn’t have those new pronouns to go by… until they did. And of course, since all language is made up, it’s not like the terms created themselves, somebody had to start by aligning themself with the terms.

So I think that:

but that probably because of my own experience.

Is more likely to be the reason why it simply doesn’t feel like you’d use they/them, had those been neopronouns.

He/him was just more expansive, and covered practically everything, so I’m assuming it’s less likely that any given individual would have wanted to switch to a neopronoun, whereas today, pronouns like he/him, she/her, and even they/them can have more societal connotations and expectations, which can feel restrictive to some individuals, thus neopronouns act as a way to break out of things like gender stereotypes even further, at least based on how I understand those who tend to identify with them based on personal anecdotal, and some light literary experience.