ME was a rushed attempt at making DOS-based Windows less DOS-like, while Vista was perhaps too extravagant in its UI. 8 is when the nosedive started and things began getting really dumbed-down as they decided to rewrite huge swaths of previously working functionality and broke much of it in the process.
11 is, according to Microsoft in their official marketing material, "the most inclusively designed version of Windows". They sure are right about that -- they included a bunch of idiots in the design process.
> while Vista was perhaps too extravagant in its UI
Vista was a fine OS. The aero glass stuff was a little on the side of bad taste, but the UI usability wasn't bad, there was little difference in UI between Vista (the hated OS) and 7 aside from visuals, the layout of UI elements was mostly the same. And in terms of look, I can't say it was worse than the fisher price styling of Windows XP. Windows 2000 is where Microsoft aesthetics peaked and it's been downhill ever since.
The main reason Vista was hated was because it was very resource hungry compared to XP and most computers could barely handle it. 7's improvements on that side of things were rather minor, and most of the reason why people loved 7 is because they ran it with hardware that was modern enough so the experience didn't feel as slow as running Vista on 1gb of ram and an intel igpu (back then, intel igpu were unreasonably terrible. If you can do moderate gaming on low settings on modern igpus, back in the day, the intel igpu couldn't even run the UI of Vista, no AeroGlass/GPU compositing for you).
Most of the truly needed architectural change in Windows for the sake of reliability and security happened with Vista, though! Vista is when the graphic stack moved back to the user space and Windows became the OS that handled GPU driver crashes best. I remember when I had an ATi GPU with terrible drivers how good it felt to not reboot the computer or lose unsaved work as Windows could restart the driver on the fly and it wouldn't cause any issue except for 3d rendering software (so games would still crash in such a situation).
Vista also virtualized some of the filesystem calls so that programs used to having full permissions to write in folders they had no business to write to could run in userspace without admin rights.
All the changes Vista did piled up in terms of overhead, making it a heavier OS, but it was all for good reasons. Some of the overhead could have been avoided if Windows had been designed the right way to begin with (like not letting people get used to running software with admin accounts) but Vista did what it could to make Windows a better OS. People who hated Vista just didn't understand how needed those improvements, which we take for granted today, were. I still remember those worms circulating on the internet instantly pwning computers just for /being on the internet/ during Windows XP's era. Installing XP from unpatched mediums like an old CD and then connecting to the internet to get updates was very risky without being behind a NAT or firewall.
I really feel grateful towards the work the Windows team did during the Vista era, that windows can be considered a decent OS at all is all coming from the legacy of the groundwork they did on its foundations.
11 is, according to Microsoft in their official marketing material, "the most inclusively designed version of Windows". They sure are right about that -- they included a bunch of idiots in the design process.