Great perspective Derek. I've always considered writing to be a skill, but the way you broke it down into many different skills makes absolute sense to me too.
You're also right about how it can paralyze someone when they try to think about how they can improve the "skill of writing." There's too much to writing to really narrow down where it is you need to improve. "Improving the skill of writing" can mean knowing how to write better headlines, or how to format your articles better. It's too broad. This is where your list of skills that fall under the umbrella of writing comes in handy.