Want an early 90s desktop with modern applications? No problems: install one of dozens of window managers, set up .xinitrc and it's just like the old days.
Have you actually tried it recently? A lot of classic Unix apps have been royally shat on by the Linux community who seemingly show blatant disregard for anyone using anything else. Many apps simply don't work correctly on a strictly ICCCM-compliant WM. Examples that come to mind - both Open- and LibreOffice will tend to dump core (and keep open documents locked) if you have the temerity to close the app via such a window manager. Firefox can't even maximise properly on some systems - it gets bigger all right, it just ends up four times the size of the screen.
Let's see… I'm typing this in Firefox 37 running within FVWM 2.6.5 on X.org server 1.16.4 and Linux kernel 4.0.2. I also use Gnumeric or LibreOffice for the office suite just fine and numerous other applications such as The Gimp, Inkscape, and of course gVim.
So yes, I have tried it, in fact, it's what I use now and have been for some time. FVWM was a very common desktop in the early-mid 90s, and still around today. The modern version is pretty much as things were years ago.
As for downloads, I get asked where I want to put something, that's how I've always done it for close to 20 years and how I intend to keep doing it.
Documents are put where I want them, not where the computer thinks they should go, this works with our business work flow, where we have separate directories for each project on a file server. A local ~/Documents tree would need all sorts of fancy synchronisation to work. Instead, we just mount CIFS from a server and throw it in there. Job done, no fuss.
Your only honest answer to the above will be, "I have no idea whatsoever." Just like 99.9% of computer users faced with the choices *you* are referring to. Apart from a small percentage of computer geeks, "choice" means "confusion". In a managed environment, the IT department will understand the choices and make suitable ones for the users. In an unmanaged environment, the user will either need to hire a professional or end up making bad choices, so it makes sense for Microsoft to make choices on behalf of its *non-professional* system users.
It's a big reason why the masses have not taken to Linux. Installing Linux usually involves making a choice or answering a question that the average home user does not even slightly understand, which immediately brands it as "too difficult".
You're right of course. We should remove all possible choice, because people find it too confusing. We should mandate that everyone's computer should be exactly the same, right down to every bit on the hard drive/SSD, look the same, work the same, have the exact same CPU, exact same RAM, exact same amount of non-volatile storage, exact same peripherals, same OS, same software.
Or perhaps you can realise that life is about choice. If they want to choose whatever desktop environment their OS comes with, they are free to make that choice on Linux. Windows and MacOS X you just get force-fed whatever Microsoft/Apple think is appropriate at the time.
I'm not saying people should be forced into choices, but they should always have the personal right to decide for themselves what works for them.
How will commecial software devs test their software against windows 10 if windows 10 keeps changing all the time?
If companies' Linux support for devices is anything to go by, I will be telling Windows 10 users: welcome to our world. A world where a company does a port of their driver to a version of the kernel, leaves it 18 months, then wonders why you're filing tickets about the driver they haven't bothered to maintain. I battled Moxa over this years ago.