> who doesn't know write

In my experience it doesn't.

It helps people who are already reasonable good at writing English to write slightly better. Through only if their writing is limited to "business" English.

For e.g. papers it's in my experience a catastrophe.

There are also multiple categories of errors it can't cope with and does bad recommendation for. It's the kinda of errors I'm doing a lot. Maybe due to having some dyslexia, maybe because it's my second language, or maybe because my brain thinks slightly different (not joking; Luckily it's just different, not worse.).