In 2018 I began rewriting Gorracula: a Tale of Science. I Gave it a main character, someone who had never existed in previous versions, rather than just expanding on an existing character. Other than that I did not set out to explicitly change anything else.
I did some extended free writing trying to find this new individual's voice and once it emerged and once this person started guiding the story it became a lot more obvious, piece by piece, what still had a place and what no longer belonged.
I tried hard to preserve my previous structure by splitting the chapters between ones narrated by this main character and ones told by an omniscient narrator. But the pieces collided and began to seem too much like I was writing two competing books. So eventually the story telling has fallen to this new character.
This voice not having been along for the ride up until very recently actually brings a fresh eye to what had become some very familiar set pieces. The basic plot structure has existed in recognizable form: shifting, expanding and chipping away like a coastline over the course of centuries, for nearly a decade now. So it has been useful to put the exposition in the hands of a fresh observer.
To extend the coastline metaphor, if you were to look at the earlier versions of this story and compare it to what it is emerging as now it would be similar to looking at 16th century maps of North America vs. ones from say, 1860. I'm not quite up to satellite imaging fidelity but at least Florida is no longer bigger than Texas and I've filled in where Oregon should be...so to speak.
As of now I have about 25,000 words of my new draft and a fairly clear plan of attack. I have a main character and an abbreviated internal timeline for the story so it doesn't go wandering on for metaphorical months and years.
Only time (and work) will tell if any of it matters.