It starts with the concept that it's essentially too hard to work on websites now without proper experience/knowledge. Except, that's because it's often a complex site or web app and the frameworks are used because of the need. If you can't work on it because it's too complicated, then you shouldn't be trying to edit it in the first place.
Their "discouraged" example under "naked html" is far more readable than the pure HTML version, and much easier to edit and maintain. There can be a lot of benefits of outputting the content using a method to generate all of the complexity and exhaustive markup.
There is nothing stopping anyone from making a basic static HTML+CSS website when it suits the needs of that site. But most often the reason why complexity is added is because the complexity is needed. Sure, there are plenty of cases where a site is over engineered, but that doesn't mean all of most sites are.
They also say that HTML is more enjoyable, which I find pretty funny. I don't know any web developer that thinks that, and I personally would hate it if I constantly had to tediously write out HTML for every little thing.