I've used a lot of computers in the workplace, and been the IT go-to guy in a dealership with 15+ Windows rigs. Not once did I run across anyone so backwards as to not be able to function beyond point and shoot. And "navigating the UI" is all that's required for Windows. Writing code, .cmd line changes, and modifying .cfg files with Notepad isn't needed 99% of the time because Windows does what it's supposed to do within the UI. That was my point, and it's the same with home users. "Within the UI" is Windows. That's why there are windows in the OS. The basic structure does the job for the overwhelming majority of users. I haven't had to dig into OS configuration for years now, and I can still generally make Windows do whatever I want. I've forgotten lots of DOS (.cmd line commands) and can't recall most of what I learned in XP, yet I had an XP Pro rig up and running and online within 30 minutes of dropping the disc in the ODD tray last week. And now I don't have to remember all those tricks and tips to streamline and hot rod XP, because there are numerous apps that do it all for me. Click, click, done.
Windows does everything a computer is expected to do, faster and easier in almost every use scenario for the average user because they are familiar with the layout. Is Linux faster or more efficient in some scenarios? Sure, of course it is. Are most PC users ever in those scenarios because Windows can't do it? Nope. Computers were supposed to make things easier. Intentionally adopting an OS that is harder to use, less universally compliant, and without universal support, makes it a non starter for billions, not hundreds, of people who want to surf the web and print inspirational quotes. And for a small business that just wants to move products/services out the door without an expensive, dedicated, IT department Linux is pointless without a major effort towards web presence/servers. And Windows can do that, too. And do that without a permanent and ongoing investment in full time support staff. Linux just isn't able to replace Windows in most real world cases. Not because it can't do the job, but because the job is already being done by Windows. If the problem is solved, why bother working on it further?
I see a lot of "once it's set up" and "when you get it installed" regarding ease of use, but "ease of use" for the average user starts when you drop the disc in the tray (or load the .iso on the flash drive). You can't just ignore that part. Install and set up are investments in time and effort that have to be considered as part of the whole. And then we have all the ways to port Windows software to Linux, or set up apps to "do what the Windows app does", find software that accomplishes the tasks that Windows accomplishes with native support...or just install Windows and be done with it.
By the time Linux is a better alternative for the average user they aren't the average user anymore. I'm not saying Linux "can't", but it's a day late and several dollars short.