I'll agree with everything here except the clean code. Clean code is about optimizing human perception and there can't be a standard for that because humans think in a wide variety of ways and it's further impacted by the level of understanding the human already has on the subject matter the code is dealing with. One person's "clean code" can be another person's nightmare.

I'll back this up with the example of Magento 1. It's a PHP e-commerce platform that has (at first glance) some of the cleanest code you'll ever see in PHP. It looked like the entire development team had come from a Java background. Every component was neatly divided into a PHP object with documented private and public methods. There was a clean MVC separation, with lots of shared behavior abstracted into "Helpers", and a Theme system handling the rendering of the front-end. I have no doubt that the authors of Magento prided themselves on how clean their code was. For them, having spent full-time careers structuring all the many features of their platform into these files, it probably did feel like a clean organization. And when I initially reviewed the code to evaluate using Magento, I also thought it was clean and was part of my choice to use it.

The problem was that when you take something as complex as a full-featured e-commerce system and modularize it so thoroughly, you end up with a literal 7000 classes, and it becomes impossible to figure out the sequence of execution of a single page request through that massive tangle. Is it "clean code" if I have to add debugging print statements to 57 source files to figure out the path of execution that renders a single page?

If I had to choose a circle of hell where I would edit Cyrus IMAP (the worst C code ever) for the rest of eternity, or edit Magento for the rest of eternity, I think I would actually choose Cyrus.