It can be the most extreme music there is.
Shawn lane is the fastest guitarist on this planet, and his music is closer to jazz than to anything else.
Allan Holdsworth plays amazingly difficult voicings, and his solos have inspired legions of players.
Even though they don't sound like anything close to shred, try playing some Joe Pass' arrangements and you'll see that they are some of the most difficult pieces ever written on the guitar.