I believe the devs that wanted/envisioned spellcrafting left ZOS. Can you imagine the complications the current team would have in implementation and game-balance?
They realized what a balancing nightmare it would be (my suspicions) and basically cancelled it.
The part of spellcrafting I think would be cool is the chance to make your character thematically interesting. Like an all flame based sorcerer for example. The bad part is that it could so very easily lead to NB's with big shields or Sorcerers with stealth.
I think ZoS realized that in order for it to be useful it would potentially blow up the game, but if they didn't make it strong it would be useless. Rock and hard place, so they cancelled it.