Like most software companies Microsoft is in love with changing the UI without any improvement in usability.
(And in the case of Win 8 a huge loss in usability!) They literally have more than a billion users that know how to use some version of the Windows UI and they feel that it is a good idea to make happy customers have to learn a new UI. The weird thing is there isn't any reason for them to do this.
As the Open Shell project shows any version of Windows works fine with any previous version of the UI. Why don't they offer an number of UIs that you can easily switch back and forth between? And how can they possibly justify why they don't do this?
(I like to call the Win 8 and later UIs the "Let's hide controls and put as much wasted white space on the screen as possible" interface!)
The biggest reason that no one wants the newer OS versions is Microsoft wants to majorly up their game in surveillance marketing after watching Google, Facebook, and other online companies make huge money sucking up all of our personal info. They are endlessly talking to us about increasing security while at the same time trying to increase how much info the OS can suck up and send home to them. Those two goals are completely in conflict with each other. Telling any big internet connected company all your personal info is the exact opposite of any version of "security"!
So Microsoft, Want me to be interested in your newest OS? Don't try to force me to log into a "Microsoft account". An online account to use a local computer is just another security risk that offers me nothing. Stop trying to make the OS require (or even need) an internet connection. I am perfectly capable of personally accessing the Internet when I want to access the internet. Stop having the OS force me to do things on my computer. You don't know how I am using it and your forced changes aren't helping. AND STOP ROLLING UP SECURITY FIXES WITH "FEATURE UPDATES". We can decide if we want "features". Security updates should just fix security issues.