Your article makes an important point. Story structure matters, along with character arc, realistic dialog, tension, theme, and many other elements and tools. World building is another skillset, as is research to make sure you get the factual elements right in every story.
Where you go astray is in asserting that good sentences are easy to write. The rules of grammar are not difficult to master, but great writing requires a well-developed vocabulary, an ear for cadence, an understanding of how to mix long and short sentences to take advantage of the impact of both, facility with figuration, and the ability to say what you mean clearly. All of those take years to master.
Many readers will forgive weak writing if you tell great stories. But writers are also custodians of the language, and we have a responsibility to treat it with respect and celebrate what it can do.