You can say they're bad design but the developers put them in for a reason. If they didn't, then there are quite a few players who would simply never stray from the beaten path and miss entire areas. Those quests are for players who desire to be pulled around by their nose ring and play open world games as if they are linear games.
I read about players who beat certain open world games in like 30 or 40 hours, then declare it good or bad. How the hell would they even know when they've only played a fraction of the content? Yeah, fetch quests are often boring and annoying, and there are players who don't need them, but I can certainly see why developers add them to the game.