Many high level players believe that the kid is ''not fully correct''. However, I think the author of the blog is at the extreme end of the position, because I'm sure the KID could be played with some effect at this level.
That said, there is no reason in my opinion for Carlsen to play something like the KID. It is risky, heavily theoretical, and simply better for white by a decent margin.
Correct me if I'm wrong, but a drawn match means the title is retained by Carlsen. Additionally, he's not well known for playing heavily theoretical openings, I think the gruenfeld is an exception here because it often leads to highly technical endgames, something Carlsen excels at.
I was looking up the Anand-Carlsen matches and came across this: http://www.alexcolovic.com/2014/11/carlsen-anand-2014-game-1.html
In the game displayed, on the move 2...g6 it is written:
"the KID is not really an option at this level"
Really?!! If it's true, then can someone be kind enough to explain why is the KID not to be played?