For a large part of end users, a "friendly" distro like Ubuntu SHOULD be a perfect alternative to Windows.
Just try to explain both Windows, and Ubuntu (with the Gnome Classic UI, I would say) to a complete noob, let's say your proverbial completely non-technical mother-in-law (with no prior exposure to Windows) ... I predict that Ubuntu won't score worse than Windows, and maybe even better.
My sincere opinion is that a user friendly distribution like Ubuntu can actually be a lot EASIER to use than Windows (easier to install, manage, use), however the public image that Linux has is the contrary: nerdy and technical, and most users have already been spoon-fed Windows and trained to use it, and so have already been more or less brainwashed in that regard ... ;-)
Fragmentation is indeed a problem, the proponents of the different distributions can be like followers of religious sects.
My advice: getting behind Ubuntu as a "de facto" Linux standard for the desktop (and maybe even for the server). It arguably has the largest community and 'ecosystem' around it and the most mature desktop implementations.
Despite my argumentation for using a "standard" I'll quickly add that I'm personally a proponent of using Gnome classic rather than Unity on top of Ubuntu, however the various desktop managers are all well supported on Ubuntu and for 95% of the apps it does not matter.
The result of getting behind a standard: wasting less time and effort on learning (and developing, and maintaining, and supporting) competing command line utilities and package managers and whatnot, more answers to be found online, etcetera.
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