I don't know if I'd consider the music only accessible to teens, but I have to say that the way 99% of djent or metalcore bands dress/act cannot and should not be appealing to anyone over 15.
Worrying about how bands dress shouldn't be appealing to anyone over 15 either.
I don't know about this whole "djent" thing. The impression I've gotten from my limited exposure to it is that it's mostly just about ripping off Meshuggah, and lord knows there's enough of that going on without a whole "genre" of bands devoting themselves to it. Might just be that I'm ignorant, though.
As far as comparing SX to it, I always got a similar vibe from the main riff of Dehumanized.