Just too fucking busy. I'd been putting it off until I read the comic, then didn't get around to it, then my parents wanted to see it. The CG is passable in the in-home sections but egregious in the premodern ones, most especially in the very, very brief scenes with Indigenous people. Unfortunately it can't cover up Tom Hanks' very not-young voice.
It probably could've been shot as a play, Secret Honor style, with the cast moving in and out on camera. But it wasn't.