If you tried hard, you could see bits and pieces of 3.1 interface in 95, but it was because you were running a fpga tool with an ancient file dialog, or you went out of your way to run progman, or an old installer launched progman for some reason (I think that sometimes happened, but could be misremembering 25 years ago). As opposed to newer windows where they change things, but not everything.
I think 95 was the last time Microsoft did user research to figure out how to make UI that is appealing and useful. At least, it was the last time they published anything about it. Newer stuff may be more appealing, but seems to make things require more clicks or wait to load more often, meaning it takes users longer to do tasks, and is less useful.
I have a suspicion that the rise of the "user experience" engineer as opposed to UI designers played a big role - they got a bunch of people, did a bunch of research, and managed to narrow their focus to "so the first time a user ever opens Word, having somehow never used anything like it previously..." and ignored "our entire company is powered by enterprise sales of this product".
Is it? That would explain why I find it confusing and moving buttons around randomly.
I had been using computers for so long at that point that I still don't feel 100% comfortable with the ribbon. It's fine, I can do what I need to do to work the programs. It's just a bit fiddly in a way the standard menus weren't. I used to be able to invoke commands with keystrokes and arrow keys. Now there's are bunch of icons on different scales, which sometimes hide if the window isn't maximized.
Pre-ribbon (and currently in LibreOffice which is what I now use), I could keep File control, Fonts and Styles, Reviewing and Drawing all on the one screen.
Post-ribbon...this is literally impossible.
XP was IMO the inflection point, where Windows started to get worse faster than it got better. And close to my heart, Windows XP was the first version of Windows that was too big to fit on my trusty Compaq Presario 1210 and its whopping 1.4GB hard drive.
If Microsoft had "stopped" at Windows 2000 (like it has ostensibly "stopped" at Windows 10), and had focused on refining that piece of near-perfection, I'd probably still be a Windows user today, and happily so. My dissatisfaction with Windows - starting with XP/2003, but especially every version after - was the big reason why I looked into alternatives like Linux.
I for one, wished for the same thing.
Alas, once Apple came out with its shiny Aqua UI (which I must say was beautify in a totally different way), Microsoft was too insecure not to try and match that. They failed miserably in Windows XP, which felt rushed, forced, and contrived. But it certainly looked more colorful.
Which is another thing that I can't stand: "Apple did something, so now we have to do it, too". Apple changed some UI element? Guess what everyone's gonna copy. Apple ditched the headphone jack? Guess what everyone's gonna copy.
You'd think that more companies would figure out that product differentiation is what makes them, you know, actually relevant amidst competition.
It seems that's the way it works for competition in the consumer market. Consumers respond to the coolness factor in a major way. Microsoft probably felt that they had to try to keep up.
As near perfect as Windows 2000 was, compared to Aqua it was also perfectly ...boring.
Come to think of it, XP wasn't even a bad start given the less than two years it had in development. The real tragedy is that Microsoft couldn't do any better for the next two decades. Windows 7 was worse, 8 even worse, 10? hopeless.
Maybe it's time Microsoft throw in the towel, admit that they have no taste[0], and go back to the Windows 2000 look. They lucked into it somehow, and it still holds up better than anything else they have tried.
One can always hope.
[0] https://www.cnet.com/news/steve-jobs-our-favourite-quotes/
Discoverability in general seems to be a long-forgotten virtue of UI/UX design. Everything insists on hiding everything now. Phones do it, websites do it, macOS is increasingly doing it, Windows is increasingly doing it, Linux desktop environments are increasingly doing it (though thankfully there are a lot of holdouts)...
The "cluttered" UI is long overdue for a comeback.
I have an old Pentium III in the basement, running Windows 2000 server, which used to be my main desktop for a while. I haven't turned it on since 2005-ish.
[0] Functionally identical to Windows XP with the luna skin disabled, as well as Windows Server 2003.