First impression is the...

DE being the first thing a common user interfaces with, it holds a very important position, in my opinion. KDE and Gnome are very different w.r.t design principles, hence the polarization and debate. KDE and Xfce are not so different. I like Gnome, but have no use for it.

I agree with all else.

Also, I think, a real "free market" would resemble Linux ecosystem. No monopoly, small players and lots of choices. However, if we wish to compete in "real world", we need to do something similar to what you say.

Linux has hundreds of DEs to suit all tastes and styles, yet it has always languished in a distant third place.

Consider the possibility that your idea of what "the common user" wants is something you made up.

Most non-technical users aren't going to remain interested long enough to try even a few desktop environments. The first one they use will leave a strong impression.

I would argue that having a choice between hundreds of DE's is a bad thing for the more casual user.

Please stop this. "Casual user", "average user", "normal user", it's all just so much bullshit people tell themselves to feel superior. Stop creating this strawman and using it as an excuse for why things have to keep sucking!

ChromeOS and Android adoption prove otherwise.

The large majority of their users don't even know what kernel is running the runtimes of their apps.

One of the reasons of netbooks failure, besides the cheap Windows XP licenses move from MS, was that each netbook Linux was its own little silo.

If we standardize we also have a central point of failure and a lack of variety/choice for users. At this point, in what way would using a GNU/Linux system be different than using an OSX or Windows system?

Because discussions are good? :-P

The big players tend to be compared, isn't that reasonable?