I think that FLOSS is a wide range of projects, and distinct ones have distinct needs. I use KDE regularly, but I understand it's probably never (unfortunately) going to reach, say, 10% of the computer users.
I used to think so, back in 2003. 10 years later, which OSS (sorta) is more successful in mass market? Android. And it has a highly closed development, and several proprietary bits.
Unfortunately, the Linux Desktop as we know will always have a niche (count me in!), but Canonical is going though a path which makes sense for a business. Who is in a game of millions of $$$, does need to control the stack.
Of course, the more open the mass products, are, the better, but I think that something FLOSS as we know it (completely community lead) will probably never pass the legendary 1%-2% share.