You don’t need to understand grammar to speak your own language.
Or rather, you don’t need to be able to describe grammar. There’s ample evidence that we understand the grammar of our native language from a young age. While it’s helpful to describe how language works, it’s not necessary.
It’s true of music, too. I know plenty of fluent speakers of music who can’t describe musical grammar. Music literacy and theory are great, but they aren’t necessary to speak music.
It doesn’t stop me from teaching theory, though. I love understanding intellectually how it works, and using that to help my interpretation of the music, for the same way I love learning about grammar when I study languages.