There are things about writing that you don’t know that you don’t know and which you would not expect to be knowable in the first place.
No one directly teaches these unknowable things because no one knows that they are knowable in a teachable way.
These unknowable insights occur as you learn unrelated things that shift your understanding of the writing process. They come in little mind-quakes that can happen while you are listening to writing lectures in the background while doing something else. Occasionally you will hear isolated ideas that stand out. The gaps between these good ideas can be bridged by a flash of insight that will leave you changed in an inexplicable way.
These insights are acquired without the ability to explain what they are but with the ability to use them to enrich your writing. It’s like knowing what radio waves were before there were any radios.
This is the writing equivalent of mysticism.