I have noticed that some people prefer to shun the rules of grammar and punctuation. They think all they should have to do is write. There is no time to spend on techniques, correct grammar, style, or for revisions. I’ve even read comments stating, “that is what an editor is for.” But that shouldn’t be the case. An editor will expect your work to be as clean as possible.
Even if you are choosing to self-publish, you should want your work to be clean. You should care what reputation you’re making for yourself. That is what your writing is building: your reputation.
By no means am I declaring to be mistake-free. Far, far from it! I’m still learning (and relearning) a lot. Sentence structure, use of commas, plot, characters, style, use of dialogue…you name it. I have been learning the craft for years now.
I guess what I’m saying is that writing is a job, a career. It’s the same as with an attorney, accountant, plumber. All professionals need, should, and possibly are required to take classes in order to stay updated in their field.
To be the best, you have to put in the time and effort to become the best.