Unfortunately marketing helps sell OS upgrades and new PCs, and one way to market a new OS is to advertise its “new and improved” UI. OS UI used to be more utilitarian and rooted in HCI principles, notably the classic Mac OS and Windows 95/98/NT/2000.

Ironically Apple got the ball rolling with fashionable UI when it released Aqua in early Mac OS X, though Aqua was well-executed, having style while still being rooted in HCI principles. Unfortunately the industry took the wrong lesson; competitors responded to Aqua’s style without providing UIs of substance. Sadly even Apple has slipped once Steve Jobs passed away; its UIs have increasingly become more style over substance. Apple has long abandoned the days of Bill Atkinson, Larry Tesler, Bruce Tognazzini, and Don Norman, and unfortunately Jony Ive was less effective when Steve Jobs was no longer around to provide critical feedback. macOS 26 is one of the biggest UI regressions in the entire history of the Mac, though thankfully it’s not unusable and it appears that macOS 27 will be a big improvement thanks to user and reviewer feedback.

When was the last time someone published a proper article that involved HCI that got even the slightest bit of attention? It's been dead for a long time as far as I can tell (last time it was alive was probably back when Win2K was relevant!).

That era ended 20+ years ago. Sorry, pal. Microsoft has been flailing since Windows 2000 to "improve" the UI, often with one bad idea after another: let's make Windows apps look like webpages, let's make Windows apps look like phones, let's remove all the graphics elements that let you distinguish one window or element from another, let's put 5 times more whitespace into every screen than is needed...

Yes, I can see where the Windows 2000 "Classic" UI was considered bland, but it was also the functional and consistent UI Microsoft ever made. Most changes since have been a step backwards.