I think it's writing as in pacing and overall plotting, knowing what is necessary to set up the story & build connections between characters while also knowing what to skip. Then, if there are no unnecessary parts, the story can be shorter and by that, drawn faster. Also, planning out chapters is easier when you have more practice in writing.
Let's take my story, as an example
I started working on it almost 10 years ago. That's a lot of time, and my writing has improved between chapter 1 and chapter 19 which I'm currently posting. And while I think my story is great and would highly recommend, if I were to start drawing it again with my current skills, I would do a lot of things differently. I'd skip some parts and maybe even characters, change pacing a bit, which would make it shorter but better. That being said, it's good as it is. BUT stories that I've tried drawing before 6,75...? With barely any writing skills? That was a disaster and took me forever to draw cx
Maybe that's not your issue tho, but that's how I see better writing = making comic faster connection.