I agree that Linux will likely never be a big player of the desktop but the reason is not technical. Marketing is the reason. Apple and Microsoft spend hundreds and hundreds of millions annually on marketing. I bet Apple spends more on marketing than the entire combined development budgets of every distro there has ever been.
I don't miss OSX at all and could not be happier running Mint.
I don't think marketing is the reason for Windows being the #1 desktop OS. It's rather the aggressive sales policy of Microsoft that literally forces PC vendors to sell their hardware with Windows pre-installed. Like "Want to get Microsoft certification for your new mobile device?" - only if Windows cannot be removed (at least that was the stance last time I read about it).
Luckily there is an easy way to counter that: enforce existing anti-trust laws! If hardware vendors and retailers were required to offer a choice of at least two OSes (e.g. Windows and Linux) to select from, we consumers would have a choice. As it is today, you are literally forced to buy Windows pre-installed, at least when buying a notebook. To prevent discrimination against Apple or the likes, hardware vendors developing their own OS could be exempt.
Unfortunately desktop Linux would still be hampered because of the lack of interest by commercial software companies to develop for it. And this lack of interest is, in my opinion, based on the very real challenges software houses are facing when trying to develop for Linux. It's in the hands of the distro developers to do something about it (or not).