We see some people already using it to automate certain sections such as emails in their life, and well.. Good luck. It could easily write something you didn't want it to or say something you didn't mean because you didn't look closely at what you were writing. There's a lot of terrible consequences of this technology and to call it a productivity hack is well, not ideal.
Possibly with a better prompt it would be better.
Writing something that fits the pattern of correct English is a very different thing for a tool to do than identifying and explaining what’s wrong with something with errors; ChatGPT by design is focused on the first, not the second.
OTOH, grammar checkers are a thing, and if you have sub-native (or even just not-particularly-formally-polished native) proficiency in a language, they are definitely quite useful (well, at least the better ones for English are), you don’t need AI for this.