[giantrobot]

> I've never used KDE but remember Windows Aero? Metro? What about macOS's Aqua UI? They use tons of resources and often times when the computer is just a couple years old it becomes unusable with the typical system bloat that occurs.

You're misattributing blame here. Aqua, Aero, and Metro were themselves just UI themes/design languages. They did not cause performance problems. To the underlying compositor it doesn't matter if a button is brightly colored beveled triangle or a flat rectangle. A 32x32px button is 1,024 pixels that need to be drawn to a buffer irrespective of what's in those pixels.

The performance problems in those UIs were almost always related to the compositor and underlying hardware (or drivers for same). Without hardware accelerated drawing, even just 2D acceleration, the compositor was limited by the CPU and memory.

The hardware limitations are only problematic at the margins though. At those various systems' introduction the performance issues were only at the low end. As the "low end" improved performance became a non-issue. Aero sucked when it was introduced because the 3D compositor was enabled on underpowered graphics hardware at the request of OEMs. Aqua ran great on then-new PowerMacs but sucked on the mobile graphics chips in iMacs and all the Mac notebooks of the time.