[Author here]
> It is my assertion that if you dialled back the Windows UI 25 years, we would actually be more productive than today,
I tend to agree. There was a sweet spot in the 1990s and it has been deteriorating since the Windows XP era, which introduced the rot of "theming" and "skins" globally as standard, hastening the end of the standardised UI.
MICROS~1 is complicit. For instance, it did a deal with Corel, which licensed the look & feel of Office 2000 (and VBA) for Wordperfect Office -- so then, MS being MS, it pulled the rug out and introduced a whole new look & feel for Office XP, which left WPO looking stale and old-fashioned.
(Another term of the deal was that Corel ceased all Linux development, which is why Wordperfect for Linux was killed, its work on WINE and the WINE-based port of WPO to Linux was axed, NetWinder was spun off and Corel LinuxOS sold off to Xandros.)
> Sorry, but UX/UI has taken a downhill plummet for decades now and it's got to the ridiculous point where I'm FIGHTING AGAINST IT
Fighting the good fight.
Teach people how to use keyboard shortcuts. Argue for standardisation of keyboard shortcuts. Accessibility is UK law and it should be worldwide law.
Document this stuff. Write how-tos and share them. Make videos. Make podcasts and talk about it.