So, I have an unusual take on this -- at least I think it's unusual.
I tend to look at "pantsing" as a tool. It's a way for me to take some little scrap of an idea and see if (a) it has enough underlying material to become a full novel, (b) if the idea morphs into something different, or (c) it's not enough to be a novel.
Even outside FediWriMo I've used "pantsing" as a way to create a treatment of a subject. I can generally tell by 20K words if the idea has enough to be a full novel, if it needs to be part of something bigger, or if it just should be a small side project (a novella maybe).
But, if the "pantsing" is successful, I will then take the more developed concept and research it, develop more lore, background, characters, etc. Then once I have the whole thing planned out, I'll start writing the new version of the story.
The example this time around was my initial concept was very much focused on a single character that was going through a mental change due to a piece of technology he'd relied on for nearly his whole life failing. The idea was to try to get inside his head and understand what that would be like.
Instead, the story has become a much bigger story about the effects of technology on people. The original main character is actually almost a side character, appearing in less than half the novel.
So, that's what I've gained from this whole experience: the knowledge that my original concept was a good one, but the perspective was wrong.