I’d argue that designers don’t even understand why they use Flat design in ui’s. The purpose, as you said, is to reduce clutter. However designers don’t understand this and remove all context from all UI elements. What is interactive and what is static is no longer discernable.
I’m writing this in Thunder and nothing in Thunder’s UI shows any distinction between text that is interactive and text that is only text. You have to click the screen at random to see what happens.
Because of this, I’d argue that Skewmorphism is better because we have had 10 years of bad UI showing that designers do not know how to apply Flat design principles.
Skewmorphism is like garbage collection for programmers. A programming language doesn’t need it and is faster without it but too many programmers for too long have shown they can’t be trusted to write clean code.