My hypothesis is today's "modern" OS user interfaces are objectively worse from a usability perspective, obfuscating key functionality behind layers of confusing menus.
It reminds me of these "OS popularity since the 70s" time lapse views:
https://youtube.com/watch?v=cTKhqtll5cQ
The dominance of Windows is crazy, even today, Mac desktops and laptops are comparatively niche
I think its more about the change management, expectations. For example in Win XP you had the option to use the NT theme. As a user: "I can decide when to move on to the new design."
Usually around 50% of your users are conservative about change. You have to keep this in mind when u change design. On the other hand, if you sell a product with subscription, you have to introduce new feature, else user will move to another product. But, when you introduce new feature, UI gets more complicated and user will blame you for that.
Like making buttons auto-hide unless you mouse-over them. I don't remember when this came in, but the default PDF viewer in something did this, and I spent _weeks_ being baffled that some jerk made a PDF viewer that couldn't zoom in on the page, until I randomly waggled the mouse for some reason and the missing buttons magically appeared. I have no words for how upsetting this was.
Like having icons-only for many functions, with no text-and-icons or text-only option to replace them. I'm sure some people are fine with that, but other people can scan a screen for a desired word MUCH faster than they can scan for a desired icon, and removal of text labels is just an insult to that segment of the userbase.
Like no longer highlighting, or even having, hotkeys for many menus. I can alt-space or alt-menukey my way through a late-90s menu tree _way_ faster than I can mouse through it, even with today's better mice, but that simply doesn't work anymore in a great many programs.
It's one thing for people who've never known a different UI to just be slow in this one and that's all they've known, and that's fine for them I guess, if it's pretty and they prefer that, or if keyboards frighten them.
But for people who have DECADES of reflexes invested in these shortcuts to suddenly find that they don't work anymore, and we're forced to SLOW DOWN and be less productive than in the past, that's a high insult.
Microsoft spilled tankers of ink in the 90s talking about how their new GUI patterns would make people more productive by unifying these things across programs (which was true; in the DOS era every program made up its own shortcuts and ways to access them), and folks who learned them are now being punished for trusting MS with our loyalty.
"Basically nothing has changed" my ass.