Harry, I do know what you mean, but the emphasis on the technical side misses the reason why the technical side is important. You don't learn to use this toolkit just for something to do, you learn it in order to communicate effectively.
I deliberately phrased my previous post so as to make the point from the perspective of a fiction writer. We bend a lot of technicalities (though we hope to have learned what we can bend, and when, so we can do it deliberately rather than accidentally), and the fact that this happens leads many would-be writers to believe the rules don't matter at all. They're wrong, of course.
If there is any hope of convincing would-be writers of fiction of the importance of the rules, it is making them understand that it's not actually about the rules. It's about communication. It is about telling your story so the reader will receive it unimpeded by the distraction of errors.
I would also disagree when you say "Until you can do that, it doesn't matter how good the content of what you're writing is." Apparently
Jane Austen suffered problems with her spelling and grammar. This didn't stop her writing great stories - it just meant that she needed help to make them presentable.
And that's really the point: Blatant errors are easily fixed - just get the right sort of help. It's all the other stuff about writing a good story that is difficult, and - from my perspective - more interesting to ponder.