My issue with this is that there's a lot of times when it's faster for me to just build the thing. And building the thing is going to uncover problems a lot faster and a lot more accurately than me sitting down and trying to imagine all the problems that may possibly occur, and then missing problems anyway because it turns out reality is way more complex than you can plan for.

Design documents are great in situations where risks are high, or where code changes take a long time to do (usually because every code change requires a design document).