To me, Windows10 is not better than Windows7. The package management is still a mess. Forced updates, no rollbacks, reboots, you name it. Permissions are also strange: why are admin rights needed to install some fonts? We still have this "Registry" with its voodoo. We still miss tools like dmesg. When thing go wrong, Windows gives some sort of simple log file, of course not in txt-form but in some proprietary format that needs it's own reader (to read some flat text, for crying out loud). The file manager ("Explorer") is still confusing. Microsoft seems hellbent in obfuscating where files are stored. Going to the terminal, the difference is even clearer. Linux offers first rate terminals; Windows look like an afterthought. Is it even possible to use a terminal full screen in Windows, nowadays? Tab completion, a decent history, pipes?
The funny thing is that Ranger, my favorite file manager, is able to give previews of files in MS formats (such as .docx) where Windows Explorer is unable to do so.... ????
Two big steps back are privacy and font rendering. It's bad enough that apps spy on me, I don't want my OS to"phone home". The font rendering is optimized for the few Windows on mobile devices users, at the expense of the bulk of the users (like me) who use it on the desktop and are now confronted with blurry fonts.
My OS must help me with my personal computer tasks. Personal means a) I want to customize the hell out of it, and b) my data is _mine_. Also, I'd like a nice readable font on my screen. Sadly, Windows10 does not meet those requirements.