I agree with everything you've written here, and perhaps I could extend the subject a little by talking about grammar itself.

What is grammar?

It depends on who you ask.

To certain traditionalists in the angosphere, grammar is a set of standardized rules issued by an authority, dictating how English must be written and spoken in order to be "proper" or "correct."

To a linguist, dictated rules have nothing to do with grammar. Grammar to a linguist means how people combine words (and other sounds) to create meaningful communication.

All languages have grammar, or they would not be languages — whether anyone ever bothered to write down formal descriptions of the grammar or not — even if every native speaker is illiterate.

Those two definitions clash, obviously.

I had a laugh-out-loud moment the other night reading an article by a respected historical linguist who broke down just how many centuries the singular they/them has been a widespread feature of English grammar.

I didn't laugh at that, I laughed at an outraged comment by a man who teaches English as a second language and who is invested heavily in the dictated-by-authority definition of grammar.

"No! No! No!" he insisted. "It's not right just because it's old! Shakespeare and Chaucer were WRONG, just like anyone today who uses the third-person plural in the singular is obviously WRONG. Being popular doesn't turn WRONG into RIGHT. Using they/them in singular isn't just obviously WRONG, any good work of grammar will tell you so. All you have to do is read it, and then you'll know."

To anybody using a linguist's definition of grammar, the above rant isn't even wrong. It doesn't make sense. It carries little to no meaning.

Of course, like all elements of all languages, English grammar evolves constantly.

So, they/them in the singular indefinite sense is as ancient as English itself. But using they/them for a specific person who doesn't identify with a gender? Sure that's an evolution, but a very small step, really, and quite a natural one — given languages exist to communicate truths about our world and ourselves.

The thing is, you can't stop languages from evolving. Just like trying to impose grammatical dictates from above is generally useless. Grammarians like the guy in the rant above have tried for centuries to stop things like splitting infinitives and ending sentences with prepositions.

Those ideas have never been native parts of English grammar, and rule books have never been able to make them so.

Grammar is.

Trying to stop it is like trying to catch a river with your fingers spread wide open.