Simplicity has no relationship to how many code structures are written or boxes are drawn. It has nothing to do with whether or not a particular person can understand some code. There is no relationship between how many "things" you can count in a system and how complex it is because it all depends on what you decide counts as a discrete "thing".
A good yardstick for simplicity, in software, is sustainability. Code that stays about as easy or hard to change over a long period of time is probably simple code. Code that gets harder to work as it evolves is overly-complicated.
Code qualities are proxies for true simplicity. They guide you because they correlate strongly with sustainability. Use them. Talk about them. Weigh them when considering your design changes.
If you want to make a change to your design and it's going to make your code easier to work with over time, don't let someone complaining that it "adds complexity" dissuade you. If you're blindly following a "best practice" and someone has a compelling argument for how it's going to make things harder in the future, you're probably adding complexity.
