-Major technical/performances issues coming from a game that didn't look that great to begin with. -Too many cliche and mediocre elements just jammed into one -Story and characters weren't good at all -Lacked in immersion. Japanese in general could learn a thing about immersion, especially when it comes to music and atmosphere. Immersion isn't blasting some j-rock with some chick singing opera randomly during fights. In fact, too many of these japanese action rpgs just have you go around killing this, then killing that, OMG YOU KILLED BIG BOSS HERE IS BIG EXP LOL" -The whole climbing on monsters thing while a good idea in theory wasn't as good in execution, basically came down to climb on a monster, mash your attacks while keeping your stamina in check. -The action and combat get praised as being amazing, but I've played MMOs with better combat. -The game length is artificially extended. If Skyrim for example didn't have good fast travel OPTIONS, the average playthrough would have been two thousand hours. DD is more of a 20-40 hour experience that they try to stretch to more with too much meaningless "walk from here to there back to here" -Not very challenging -AI pawn henchmen instead of being able to have friends take that role in an RPG in this day and age is pretty stupid. Skyrim can get away with it because the game doesn't use "henchmen" as one it's selling points, in fact, most players don't even use them. Skyrim is also a MASSIVE dynamic world with thousands and thousands of quest lines DD isn't. The basic questlines in DD are like "go kill 2 goblins ok now go kill a hydra over there lol" -Wonky AI from the enemies and your pawns.
To sum things up, the "unique" features and selling points of this game weren't all that to begin with, and the whole experience comes off as very generic and mediocre at it's very best, and pretty awful at it's worst.
Yet it gets rabidly praised here on this board simply because it was made in Japan.
It gets praise for being fun. Sorry that it couldn't be Skyrim with multiplayer. Because that's what you seem to be asking for. You talk about it being easy but bring up Skyrim more than once. There hasn't been a challenging Elder Scrolls game on console.