The purpose of documentation is communication. It's a way to communicate to the team working on the product and future teams working on the product. Too little or too much documentation, and the communication breaks down. The right level of documentation is based on how effectively the team communicates and the overall velocity (user stories being completed).
Recently we asked a team to include a screen mockup and user experience diagram as part of the definition of ready. With these diagrams, we noticed developers spending less time estimating, planning, developing, and testing. To the typical Agile practitioner, this was the completely wrong approach, and just having a conversation would be good enough. However, discussions were more efficient with the diagrams as developers spent less time understanding the user story. The team achieved a greater velocity.
You had a thousand pages of stuff to go through, right? Not so much. A screen layout and a user experience diagram were displayed on a single page— basically, two pictures. Pictures are were worth a thousand words. Ask the question: How can you best communicate to move the product development forward quickly and efficiently? communicate to move the product development forward quickly and efficiently?