Oftentimes, I could've built a product from scratch in the time it takes me to Google the undocumented quirks of some stupid YAML file.
You can do all of these things with 100% test coverage, but that doesn't relieve you from dealing with the weight of the architecture and extra work when you try to add or change functionality later.
This days if I have a static site around 10 pages, I just use .Net MVC project and use partial views to store the content. Much easier than using a CMS and I still retain all the control I want.
Replace YAML with XML and you've just described every enterprise software library I've ever used ever.