As fantastic as modern word processing apps are, with spell and grammar checks, there is no getting around proofreading your own work.
No app will catch that you meant to write the word "bones," when you forget the b. "Ones" is a noun, after all, and it's correctly spelled, so no app will catch that it doesn't work in the context. Only a proofreader will.
You can never have too many eyes on a MS.