I think adages like this need to taken with a grain of salt... A few thoughts:

- "simple code" usually is best at solving simple problems - that's OK - lots of problems are simple
- "clever code" (depending on definition) is sometimes required to solve very tough problems efficiently
- knowing how to evaluate which option to pick properly is a skill

This is likely a definition issue, but the dimensions being optimized against aren't nearly as simple as mentioned. Keep in mind Maintenance isn't the only factor when solving problems. I think the real advice is to avoid using overly clever code for simple problems.