LLMs, when trained on a language, provide a neutral representation of the statistics of that data set. Used correctly, that makes them perfect for this kind of task. You're reacting to global misuse of llms as databases, but llms as language models is what they are designed for. It's in the name.

Used judiciously as a model, there's no problem. They only become a problem when people try to treat them as a database.

I mean, it's what it says on the tin: linguists go into remote areas and take recordings of dying languages to preserve them. They'll sometimes prompt for specific words and sentences, other times just record people speaking naturally. Then they'll also write down the rules of the grammar and the vocabulary (another example of using a medium they may not themselves have).