I dont think people hate it, but its not "meta", and people like meta. Arcane in comparison to fire has several disadvantages - you have no safety net (cauterize), you have to be constantly in melee, which means you generate a lot more threat (in higher keys most stuff is kited and you will mess up the threat table if you are in melee), any cleave can more or less 1shot you, and one common issue i find is no matter how good the tank, arcane is VERY bursty in AE which can just get you melee slapped.
The best AE build is also with shoulders/AO, which travels all the way to Dalaran and can pull random packs no matter how careful you are.
Yes we are squishy but we also have block, barrier (with 15% mag. dmg. red.) and invi with 60%? dmg reduction.
No, we are not in melee range. You can stay at 15y and do your aoe rotation without problems. And if at that distance you get hit by something then you have to learn to position yourself and dodge mechanics.
And yes, shoulders are going to pull everything like a hunter if you dont know when and where to use barrage. The only place that you have to be hyper-careful its on lower kara where the walls are f**k up.
One tip if you want to use barrage to proc. shoulders but you dont want to pull the next trash pack. Blink behind the mobs, turn around, use barrage, go back with displacement or stay there if you can. Always aiming to where there are no packs.