Just to tell you I'm not a coder, I'm a designer and artist who happens to like coding as it's also a creative process. I used Tpyo3, Wordpress, Joomla, WebEdition, Modx and other CMS when starting with CMS's. I barely could code php. I only struggled with those platforms and had to deal with stuff I didn't want to, be it security issues or updating, learning something arbitrary platform specific. Modx happen to be a tool I worked with before ProcessWire. Within days and many hours I had a prototype of a module which didn't do anything other than say hello. All those system never really let me do what I wanted without getting in the way or installing some plugins that didn't work really. It's because they're too opinionated to be useful in a wider range of contexts. They're all cluttered (I think you got that all wrong). Which all lead to frustration and hours and hours of wasting fighting a system. They try to save you time but in fact they put you in constraints that often make little to no sense. Now all those systems try to solve certain issues by putting yet another layer of complexity and so on.
Then I discovered PW and finally I was in charge, saving time, focusing on things that really matter. Within an hour I had my first module "HelperFieldLinks" working without even reading a manual other than the HelloWorld.module. It's so simple, it didn't take me long to see the simplicity and power of PW. I am able to put contrains where the project demands and not the system. It's all so simple even I could as a non coder. PW makes me shine, and people think I'm a good coder. lol. So wrong.
I have built websites for my mom and sister, and never had to explain or show them how to edit their site, they found out them self, which speaks a lot of the usability of PW.