After shipping my first game I realized my game design doc was hurting me more than helping. Anyone else?

I spent about eight months writing what I thought was a thorough game design document before touching a single line of code. Mechanics, progression systems, lore, economy balancing, all of it. Felt really professional and organized. Then I started building and within two weeks half of it was already obsolete.

The thing is, writing the doc felt like making progress. It scratched that productivity itch without actually forcing me to confront whether any of my ideas were fun. When I finally had a playable prototype, so many of my carefully documented systems just didn't feel good in practice. I ended up cutting maybe sixty percent of what I had written.

I'm not saying documentation is useless. Notes help, especially when you step away for a few weeks and need context. But there's a real danger in treating a long written doc as a substitute for actually prototyping ideas early.

My current approach for project two is documentation after validation. Build a rough version first, see if it feels right, then write it down so you remember the decisions you made and why.

Curious how others handle this. Do you document heavily upfront, or do you prototype first and document later? Has anyone found a middle ground that actually works on a solo or small team project?