I spent six years teaching English in Japan. I didn't work within the education system, but for private conversation schools. Mostly solo or in small groups, my youngest students were around 3 years old, while my eldest was well into his 80s. It was fun and interesting, and very educational. Those students, who had been studying English since they were in primary school, had varying spoken abilities, but generally their grammar knowledge was far in advance of my own.
I recall the first time I was asked whether a particular word was the 'past participle' or not. I panicked, not even knowing what that meant.
But during that time I studied and learned and picked up a great deal of grammar.
By the time I went to university to study English teaching, at the ripe old age of 37, I knew much more grammar than my fellow students. This certainly served me well, and I can remember a couple of time I was asked by the tutor to explain a concept to the rest of the class. EFL experience helped a great deal.
Now that I write none of this knowledge and experience is wasted. I don't always get it right, and there are times when I've written something that's more obvious to me than my beta readers, but generally I'm told that my pieces, even the first draft, are very clean.
Personally I think a writer should be interested in language. As an English teacher I encourage my students to develop more sophisticated writing styles and reading habits. I also try to engender a love, or at least an appreciation, of words and language.
Sometimes I even succeed.