Hm, dunno. I'd say writing is about having something to say. Especially something other people want or (more importantly) need to read. I don't think that Charles Bukowski was particularly disciplined or educated for example.
Regarding Bukowski, you should check out his Wikipedia page. I'll snip some highlights, and draw some conclusions.
https://en.wikipedia.org/wiki/Charles_Bukowski
> poet, novelist, and short story writer
> Bukowski wrote thousands of poems, hundreds of short stories and six novels, eventually publishing over 60 books
You don't write thousands of poems without understanding language. He may not have had a complete collegiate education, but you can be sure he ended up studying language on his own.