The KG is sound if you ask me...
It's just too scary for top level GM's who live and die by their rating these days to play it when Nf3 is just as good.
For those that really believe Fischer's refutation lives up to it's name... yes, he was on to something but as a KG player I can tell you that I LIKE (emphasis on Like!) playing against the 'refutation'.
3. ... g5 is a lot of fun to play against too.
Just keep that in mind when you play the black side of the KG.
"And if you face 3.Nf3, there's no point defending the pawn at the cost of ruining the kingside pawn structure with ...g5?. "
Yeah. What's to be gained by blindly following those silly main lines?