It surely doesn't.

I played the a6 Slav for many years and just couldn't learn the Semi-Slav.  It just bothered me to try to learn all that theory, but when I discovered the KID about a year ago I fell in love.  It has everything to do with taste.  My game is better tailored to lines in the Mar del Plata or Classical, and sometimes I struggle against the Saemisch or early Bg5 systems.

At any level short of super-GM all openings are pretty much playable, methinks.  KID is dangerous for both colors in my opinion, but that--my friends--is chess.  Some of us like to live on the edge of our seats.  Some like to grind.

I do think the biggest difference between the KID and Semi-Slav is that the KID involves accepting what is often a positional liability for a safer king and clearer attacking plan, whereas many of the Semi-Slav positions involve either giving up some initiative for a solid structure (Meran, Anti-Moscow) or giving up king safety for an open/attacking game (Botvinnik).

Whoever says that the Semi-Slav is more solid than the KID has never had 5. Bg5 played against them. Even the Meran lines are tough. The KID is positionally risky, and Black also risks a lot if White is well prepared. For some reason people only think the KID is the Mar Del Plata, which is not true. Would you like to play against the 4-Pawns or the Samisch when you're unprepared?

I think with regards to difficulty, they are both quite theory heavy, and both also the more acceptable albeit risky choices for Black. Very similar in risk and reward, as well as required knowledge, but very different positions. It's all about what you think is best for you.