As the title says, the dungeons lack "soul", they are just bland, simple and boring, I know how people react when one compares this game to another but let's just do that, let's take World of Warcraft or The Old Republic, each dungeon was its own identity, you can tell from just looking from a glance where you are (ok, in some cases you can tell not the dungeon itself but the area where the dungeon is located), if not from the looks then from the sounds...
ESO has none! The dungeons are simple, boring re-used assets, and talking about reusing assets, the bosses, they are just bigger copy-paste versions of other mobs in the game, why?!
World of Warcraft is the Pinnacle of Dungeon Grinding but at least they are aware of that and they make very distinct dungeons and boss fights to compensate for that, ESO does not even try! The dungeons are always some dark. moody hole in the ground and that's about it...
It's no the bugs, not the combat, not the lore... you can make a perfect game in terms of mechanics, of story, of gameplay but if you offer the exact same thing over and over it just gets boring...
And that is what I fear most about the future of this game, the lack or diversity and originality, the game is getting stale and it's not even one month old.