You will get 50-80 hours out of it.
Damn. As bad of a review as you push forward, this alone should make the game an insta-buy for most gamers. Vast majority of AAA titles give me 12 - 20 hours of gameplay.
I agree that the "end game" really falls apart though. Everyone I've talked to that have invested much in the game have complained about this. The game feels really immersive and magical in the early levels of the game, but Bethesda could have done a better job at making some kind of an "end game" worth playing.
What bugs me the most about Skyrim is that there really are no factional relations stats of any kind. Your actions should lead to someone somewhere being ###### off at you and not wanting to help you. All the quest lines are very linear and few have decisions that lead to consequences larger than the outcome of the specific quest you are working on. Nobody in the world of Skyrim seems to give a flying #### that you are carrying around a countless number of "evil" Daedra artifacts that you no doubt had to do something slimy to get your hands on (for example).
I could pick Skyrim apart bit-by-bit just as you have done here. My friends and I have sat down and all had this discussion years ago when the game first came out (yes, I'm kinda poking you for a late review of the game). Despite that though, we have all come to the conclusion that it was a great game that was filled with many hours of enjoyment.
A lot (but not all) of my issues with the game have been resolved via modding.