> No?

No.

Rendering outside of a web browser gives you a lot more freedom when it comes to how you layout and render. Rendering engines don’t necessarily use components tree by the way.

Even gui frameworks (which is what I think you are talking about with OS graphic library) have layout engines which are a lot more powerful than css. Flexbox is a step in the right direction but still inferior to what some frameworks could do 20 years ago.