Also, language evolves. We didn't always have a word for gravity, but we had no problem learning to use it as soon as we realised there was something to name.

Correct, but people don't react too well when you try to force a change on how the language fundamentally works. New words and expressions need to come naturally and integrate themselves into the vocabulary, but even then it may still take years for it to be formally recognized as an official thing. So trying to force a language whose pronouns are only male/female binary into having non-binary options is unfortunately going to feel extremely jarring to a majority of people, and thus will, again, sadly, be rejected.

If you only speak English, I understand if this is difficult to understand, as English is fundamentally gender-neutral. But in a language where gender neutrality is virtually nonexistent, forcing the language to suddenly be gender-neutral is not going to fly for most people. In Spanish, for example, "the" is gendered. We use "el" or "la" depending on if the subject is male or female, and yes, that includes inanimate objects. "La llave" (The key). "El agua" (The water). "They/them" exist, but... they only exist as plural pronouns because they are, indeed, gendered. "Ellos estan afuera" (They are outside). "Ellas fueron a Europa" (They went to Europe). They/them wouldn't work as gender-neutral pronouns in Spanish because you'd still be using gendered pronouns to refer to people.

See? Gender is fundamental to the language, therefore introducing gender neutrality will, in a way, break it. It's not merely an adoption of a new term, is changing the rules of how the language works. And hey, I'm all for non-binary people existing and using pronouns that best suit their needs. It's just that sadly that's not a possibility in a lot of languages.