In my understanding: Complexity = Userunfriendly UI or the system used in the game people started with in a series. Or at least that is the impression I am left with after discussing the changes from Morrowind/Oblivion to Skyrim.
Personally? I agree that the sysytem is simpler to use than before, but that doesn't meant it have less depth.
And there is the issue of the character system which is always brought up sooner or later in these threads: Having limited amounts of perks and increases to your primary stats will, from a neutral point of view, allow for more varied characters than the attribute system used in MW and OB unless you count it as a different build that one character have 99 strength and the other one 100. Classes are no longer a thing you chose, but guess what? Every playstyle is still there, with the exception of acrobat and marathon runner.
I would say that they streamlined a lot of things, but that isn't necessarily bad. Problem is that the fanbase of any game will always riled up against any change whatsoever to their beloved fanbases. The are some who will go to the extreme and say that they stripped the game of all its rpg elements (this statemente is clearly false), but that's just their way of saying: "I played Elder Scrolls games before it was mainstream."
I sense a lot of truth in this post.