Don't call yourself stupid for writing readable code. Based on my opinion writing readable code is very smart. Why?
  1. Having easy readable code means you can jump in and start expanding it at any time without spending time to relearning of how that code works.
  2. Easy readable code would also give you better starting position to start working with someone else in a team since they will understand your code more easily.


Also not being able to understand some less readable code also doesn't mean that you are stupid. it only means that you have still something to learn.

The only time that you should call yourself stupid is when stop learning because you think you can't learn either because you know everything or because learning seems to hard to you. So keep learning.
I myself am an educated market salesman and komercialist but I still leaned about programming on my own to the point that I would probably be able to teach others a thing or two.