Kind of reminds me of editing projects, communal course design discussions, and other collaborative work I’ve done in the past. And yes, this is why writing is a solitary activity so much of the time. And, I suspect, why the book is usually better than the film.
This is why crit groups are useful, too. Because crit groups are almost always full of other writers, meaning, people who are both readers, but also know something about writing.
But it always becomes a solitary activity again, in the end. Because crit groups all too often bombard you with dozens of great ideas, of which you can only implement a few. This is not a criticism: I love my current crit group, and loved my past ones too — the self-organized ones, anyway. Some of the classroom crit groups were, well, so-so. But no matter how great your friends’ criticisms are, you still have to decide whether Sarah and Henry divorce at the end of Chapter 2, whether one kills the other, or whether both of them have sex with a shark. (But don’t fall in love with Jaws. Not that.)