Modern UI design is awful. It might work for Joe Moron, who is just scrolling through video clips and short fragments of text, but I can't imagine why you would ever try to apply design principles designed for that case to professional users. Do people really think they can take the complexity out of these inherently complex business systems? I'm not saying that everything has to look like shit, but no amount of dumb…
Well, let's challenge ourselves: what is the best designed (digital) interface with the deepest usability? Or some outstanding interfaces that square that circle? I'm familiar with 3d software suites, and they're (mostly) all highly-configurable, permitting custom layouts, panels, toolbars, and even enabling intermediate users to create UI tools. To your point, they're also ferociously complicated for novices. Bloomb…
3D software suites like 3DS Max or Blender are perfect examples of software that's a tool, not a toy. The learning curve is roughly proportional to the breadth and complexity of the problem domain, so training is required, but the software itself doesn't waste your time and patience with slow and low-density UIs.