Knowing how people will use something is essential

Isn't one of your first exercises in learning how to communicate to write a description of how to tie your shoelaces? The point being that it's basically impossible to use text to show that

The hardest part of design ... is keeping features out.

It was always amusing to be inside Apple and read what journalists said we were doing

A challenge to the designers of the world: Make signs unnecessary.

I prefer design by experts - by people who know what they are doing

If you think of the product as a service, then the separate parts make no sense - the point of a product is to offer great experiences to its owner, which means that it offers a service. And that experience, that service, comprises the totality of its parts: The whole is indeed made up of all of the parts. The real value of a product consists of far more than the product's components.