There's a subchapter in the book called Dense UIs have their place in which the authors mention situations where more compact and busy design is more desirable, adding a screenshot of a sports results website as an example.
The rules in the book (and on the website) should not be seen as set-in-stone, they are more principles we can follow depending on the situation. I think the use fewer borders principle is very useful in many scenarios.
Saying that, I agree that today's designs tend to too much whitespace (there was a blog here recently ranting that all product landing pages are basically a navigation bar with a shallow text over a picture background).
The rules in the book (and on the website) should not be seen as set-in-stone, they are more principles we can follow depending on the situation. I think the use fewer borders principle is very useful in many scenarios.
Saying that, I agree that today's designs tend to too much whitespace (there was a blog here recently ranting that all product landing pages are basically a navigation bar with a shallow text over a picture background).
You can check this blog if you want to see more principles from the book: https://medium.com/refactoring-ui/7-practical-tips-for-cheat...