Desktop pretends to be (or maybe they actually believe that's what they are creating) a product for end users but is a product for admins and developers who are familiar and comfortable with the UNIX-like environment to use on their personal computers.
This is total BS. Lots of people who aren't computer experts use Linux desktops every day. My wife is one of them. I never have to do anything much with that computer, besides regular backups of course. Back when she was running Windows, I had no end of problems with it. I'm sure plenty of people here can attest to similar stories, of switching their spouses or parents to Linux and no longer needing to spend any time being their unpaid tech support.
What desktop Linux is, is a very good product for people who don't need to run any Windows (or OSX) applications. For home users who just surf the web, use Facebook, and do basic PC tasks like some basic word processing or whatever, Linux works extremely well. For people who just *have* to run Photoshop or whatever, obviously that's a problem, but not everyone is like that.
The Linux desktop community is a mess of hundreds of different distributions, various different protocols for doing things (how many freaking sound subsystems do you need?! ALSA, PulseAudio, FFADO, Jack, OSS, etc...) and all kinds of different UI paradigms, frameworks and toolkits.
You're completely overblowing things. Most modern Linux distros have settled on ALSA and PulseAudio (ALSA is the kernel-level drivers; PulseAudio is a userspace layer on top of that) and it works fine. No one uses OSS on Linux any more, and Jack is only used by a small number of people doing high-performance audio stuff. Different UIs aren't a big problem; people get along just fine choosing a desktop environment like KDE or Cinnamon and sticking with that. Different toolkits don't matter if you aren't developing software; you can run software written in one just fine in a DE written in another.
The problem with that is that the vast majority of computer uses do not want to choose every different option for every different part of the operating system
And they don't need to. Just download a copy of Ubuntu or Mint and be done with it. That's what everyone else does. This choice is generally made by the person who's computer-savvy, and the user doesn't question it. My wife uses KDE because I chose that for her since I prefer it and it works similarly to Windows, and she's never had a problem with it. She doesn't know or ask about Unity, Gnome3, Cinnamon, MATE, Xcfe, etc. People have zillions of choices when they buy a car too, but regular, everyday people don't have a problem there. They pick something they like and stop worrying about it. It may be a car their friend had, or they may have just stopped at a dealership and checked out a few things based on a salesman's advice. No one checks out every single model of car before making a decision.
yes i know you set it up for your grandma and she likes it -- represents falls outside the vast majority).
No, actually it doesn't (BTW, your sentence doesn't parse here). Most home users don't do anything terribly complicated with their computers, and these days they really don't do anything besides use it for web-surfing. This is why tablets have become so popular: people are sick of Windows problems, and tablets work just fine for using Facebook. Linux works fine here too, and better than tablets (since you get a real monitor, a real keyboard, real storage space, etc.). For the things most home users do, Linux does them extremely well. It can even play a lot of games now too, though that still works better on Windows because many games still don't support Linux (including anything that isn't on Steam) of course. No, it doesn't do TurboTax, but who cares: everyone's moving to web-based stuff for that. No, it doesn't run Pro/E, but how many home users do that. I've never heard of someone's grandma running engineering software. No, it doesn't run [random Windows software], but neither does Mac OSX, but I never hear of anyone saying Macbooks aren't viable alternatives.