Jordan Klepper (correspondant on The Daily Show) talks about improv and writing on episode 4 of The Daily Show Podcast.
He hits on the idea that in the writers room you may throw out a dumb joke that would never work, but people start riffing on it which leads to the polished joke.
The same thing happens with design. You may put together a design that doesn’t work. But you keep iterating on it which leads to the right solution. I’ve also put together designs that I know would never make it into production because they’re too far off the style guide or unrealistic to implement. But often ideas come out of that work that I wouldn’t have gotten to otherwise.
Executing on an idea is never a waste of time. The only waste of time is never executing.