Shredding is more fun to do than to listen to perhaps. If you can't do it then don't knock those who can. Maybe it's just a jeaolousy thing... I enjoy being able to widdle and wail like a sick thing and run tapping arpeggios off at 16 notes/second.
There is such a thing as superflous technique though.

There are higher arts than shredding, like being able to play multi-part melodies by tapping or fingerstyle.

Some techniques are difficult but do not qualify as shred, like playing a G shaped barre chord or violining pinch harmonics.

As for not playing whole tunes with pinch harmonics, why not? That's like saying a melody cannot be played in a high octave! Pinch harmonics aren't really shred are they? With practice you can alternate and even sweep pick them. I thought shred meant speed, like fast notes or fast vibratos.

For me technique's always been something to practice while waiting for musical inspiration to come.