From what I know, it only has minor under-the-hood changes from Win10, while having MASSIVE regressions to UI/UX. Increased ads, increased spying, and while certainly subjective, I think the largest regression is how much it's trying to imitate MacOS.
News flash to Microsoft, there are a lot of users that use Windows because it's not MacOS.
I can't think of a worse UI change than what Microsoft did to the right click menu. I'm ok with UI changes and will randomly try different WMs on Linux but that change was just SO frustrating. Zero benefit, loads of friction.
The worst offense is that the taskbar, which now is forced into removing labels and forcing grouping of tasks. Gone are the days of clicking Firefox(Window 1) and Firefox(Window 2), they've just copied the mac dock.
Yes you can use registry hacks/tools from github to get the functionality back... but this is just unacceptable.
For what it's worth, some of the spying can be disabled with O&O's ShutUp10 [1] One needs to run it after each windows update and it will show you what if anything under its purview has changed. Disabling some telemetry can make the desktop a little snappier as it is not phoning home every time an application is launched.
There are also a bunch of PowerShell scripts on github that do the same things but some of them change risky options that can break things so I will not link to those.
I've heard a rumor that much of the modern windows UI is planned out by designers whom are all apple ecosystem. Looking at the win 11 settings menu, and at the surface laptop, it's clear they're copying the success of Apple. This is what happens when there's not a central vision for a product. It's all user studies and data psuedo science that just reflects what average users want - apple products.
News flash to Microsoft, there are a lot of users that use Windows because it's not MacOS.