So first of all i just want to say that i understand there is no "best UI" when it comes to Windows, same as there are no best AV, and that it depends on the user's use and taste.
So what i'm about to say is just my personal opinion based on my personal experience.
First i totally understand you and you're far from being alone. In the 90's, UIs where kind of "boring". Windows 95, 98 and Millennium where almost looking the same. Also back then all UIs had a square design with no (or very few) round borders. At that time i was pleased with that as that was the only UIs available and i never gave much thoughts into it.
Then came Windows XP in the 2000's, and probably what is the best Windows in my opinion along with Windows 7. XP had an amazing look for that time, with lots of round corners, joyful colors (without being childish) and was light on the system as it didn't had effects such as Aero. And not only Windows but most OSs followed that trend. At that time, i though the future of UIs would be soft corners, better effects and such. I would never have thought in the 00's that any company would bring back a square design UI as for me it was a thing of the past.
Then came Windows 8. Oh boy, probably the worst Windows along with Vista in my opinion. That OS will stay in my mind as probably one of the biggest fail of all time when it comes to user interface. I mean, how could you make it any worst ? To access the desktop you had to click on a "tile", as if it was an app. No more start menu with nothing that was really replacing it. And of course back to the pure squared windows, with zero 3D design and zero effects such as Aero... I know i'm bashing that OS big time, but Windows 8 felt like Windows 98 stripped out of his start menu and with a lame full screen app menu on the top. And i'm not even talking about Windows 8.1 and their "incredible" start button.
When it comes to Windows 10, i'm honestly used to it and it is "technically" the best Windows. It's incredibly light, has excellent out of the box protection, has very good self maintenance tools, good native apps, provides access to the app store catalogue while still relying mostyl traditional softwares, syncs your settings, etc... And what makes Windows 10 great is that, unlike previous Windows, Microsoft is constantly adding functionalities and improving it. And i have to agree that even though the UI is very minimalist, it is very clear and straight to the point. So i'm really used to Windows 10 as of now and like it.
But i can't help having mixed feelings about Windows 10 and today's UIs:
- on one hand I like how practical and easy to use is the Windows 10 UI. And it's true that OSs nowadays do offer very optimized UI that have been polished and improved over the years. So much so that i doubt we will see a big change any time soon, regardless if it is on Windows, Android, iOS, etc...
- on the other hand i do miss the extra Aero design and the fact that any kind of design or fun has been stripped out of the UI. And why do these Windows have absolutely no rounded edges ? Probably because it is "optimum", but i can't help but feel it's a step backward.
But i guess the UI of Windows 10 represents the state of today's society when it comes to technologies. There is little place for the "fun factor" nowadays and it is all about being optimized and practical. Take smartphones for example. They are designed to have the biggest screen and most features in the smallest body. Are they useful and the best for everyday use ? Yes. But are they fun or unique ? Nope, they look just like clones regardless of the model or brand. While mobiles phones in the 2000's where all about having polyphonic ringtones, interchangeable cases, unique designs, fun accessories and such.
For better or worse, from software's UI to our daily tech, we are heading to a more optimized and practical future at the cost of losing originality, fun and uniqueness.
Here are some pictures to illustrate the today's practical but bland VS the old unique but less convenient i was talking about:
Windows 10:
Windows XP:
iPhone 8:
Nokia 3650: