There's a lot of degrees from can't speak any language to master of English.
LLMs aren't babies, they're not masters of the language. But, they'll clean up trash English to something that is better. I'm thinking of all those StackOverflow questions where the OP couldn't find the shift key or any punctuation. Even lazy usage of an LLM would be an improvement. If you're writing for high stakes professional publication, you probably still need a human professional.