Without having played Witcher 3 yet (it's downloading as I type) I suspect that this is mostly a matter of presentation. As far as I could see from various videos I've watched, all sidequests in W3 have cinematic dialogue, a proper cutscene and a couple of more lines of dialogue all in all. I'm pretty sure that if you gave the infamous "Templars killed my husband, bring me back the ring they stole" lady cutscenes and more dialogue, more options for the Inquisitor to react ("F*** Templars how could they do that!", "It's your fault for staying here, there is a war going on lady!", "You really should leave the area!", "I got your ring back but how about some contribution to the Inquisiton effort?") the sidequest couldn't be so easily devaluated as "senseless fetch quest". I feel like this is something the Witcher 3 does much better.
Or take the bear "ass" fetch quest - how about a cutscene when the Inquisitor finds the item that starts the quest? Cutscenes of heroic bear slaying? I bet that quest would have attracted far less criticism.
The more I think about it, the more I'm convinced it's not the fetch questy nature per se (obviously, because most quests in all games are fetch quests at their core) but the (lack of) presentation that makes them seem unimportant and thus make them a target for criticism.
Disclaimer - I love, love, LOVE DA:I. It's one of my favorite games ever made. I also fully expect to love Witcher 3. It's almost unfortunate that two great (and successful! never underestimated that!) games like these release so shortly after one another - where am I supposed to take the time for both? I'm still not done with DA:I! A great problem to have I think. Also (again, without having played W3 yet) I bet the DA team will have a close eye on the things Witcher 3 does well and I bet we'll see some of those things incorporated in DA4 so it's a win for everyone.
(and now I'll bow out of this thread because I really fear Witcher 3 spoilers)
It's more than just cutscenes. While the quests DO have far more cutscene and cinematic content there is also a great deal of clever design involved in the quests themselves and even when the same features are re-used (hunting monsters by speaking to witness and tracking the beast) each quest is designed in clever and involved enough way to feel fresh and interesting.
There's just no comparison in quality.
A lot of this derives from how the investment in TW3 is different. There's no multiple PC VO, Geralt has far fewer conversation options per scene, and there are no companions. If Bioware could cut all of that content to put it toward side quests DAI would have been a radically different game. Just saving the 5 hours of banter VO costs would have been huge for side quests.