That says to not be creative just to entertain yourself. Be creative to solve problems. It is a polite way of saying "you aren't as smart as you think you are at 3am on a red bull binge". This advice was not invented by Google. Knuth or someone for one has a famous quote about it: debugging is harder than first draft, so how do you debug code that you wrote at peak cleverness?
From The Elements of Programming Style by Kernighan and Plauger: “Everyone knows that debugging is twice as hard as writing a program in the first place. So if you're as clever as you can be when you write it, how will you ever debug it?”
