Alright, I think I have found the main point of our misunderstanding:
> The main benefit, and the whole point, of layered architectures is to ensure the software architecture to simplify modifying/updating the bits that change very frequently and stabilize and minimize the need the fundamental bits that only rarely need to be touched.
The thing is - "onion/hexagonal/clean" architectures and "layered architecture" are not the same things.
Of course layers are fundamental - nobody questions them. What I do question, are 3 mentioned architectures.
For example MVC is also a layered architecture, and in many cases it works great. It allows the same level of testability as hexagonal architecture, but with less boilerplate and indirection. It is great for building websites like this forum.