Frankly I found Shenmue on DC to offer more interactivity within it's map than GTA 5
While I enjoy Bethesda games, they just reuse everything over and over again. Every "dungeon" is the same, every town is the same, every npc is the same, every voice is the same, everything is rehashed over and over again. It gets boring after a while. Looking at the same textures on the floors and walls for every cave I enter gets old. Regardless, they are still fun games.
I believe it was stated that all the dungeons are hand made. I don't recall seeing any dungeon that was the same as any other aside from the fact that they are dungeons...you can't expect too much out of a dungeon/cave or any under earth dwelling. In Oblivion they even stated that every stone is different but dunno how true that was.
All games rehash textures, even Rage with it's virtual texturing, despite the marketing still rehashed everything with their stamp tool over and over.
A lot of what you mention I blame their use of their rehacked version of the Gamebryo engine. Other things like voice actors could have been limited due to budget, I'm sure it takes a huge budget to make such a deep game like Skyrim.
Let's face it, Skyrim has over 300 quests and more if you include DLC's and they all have some very nice variety to them unlike AC series or GTA series.
I'll still never forget the painting quest from Oblivion, it was unique. Others are trivial like passing along a message but at least there is some variety and plenty to do at every corner.
Overall I think we're limited still by technology to offer a truly open and interactive world but Bethesda games seems to come the closest.