Comparing an MMO to a single player sandbox game is laughable. Also illusion of freedom pretty much DEFINES the video game experience. Conversely I find MMO's to be pointless grindfests defined by level grinding disguised as immersion and content depth and an end game that if not for elitists would be still be nothing more than a tedious version of playing doll with your in game graphics.
Actually, a MMO is a much closer comparison to Skyrim then non-sandbox RPGs.
1) Very little storyline? Check: you have the MQ (4 hours tops altogether), and you have one of the two copypasted (up to the dialogues) civil war faction. The rest is empty and feels rushed (Im Archmage after running half a dozen errands? Wait, what?)
2) Very little ingame roleplay? Check: you have no way to decide what kind of answer your character gives, nor any way to decide on how to achieve or complete quests/tasks, and nothing you do has a lasting impact on the world anyway, which in turns destroys all sense of personality developpement. People have said "do it in your head", but it was kinda hard to imagine I was not beating this old woman as my character was pounding on her because the only other option was to abandon the -entire- guild quest chain (supposedly about honor too...).
3) Tons and tons of generic repetitive quests? Check: Go fetch this, go give this to that guy, go kill this guy. Hundreds of storyless, unimaginative quests with no feeling of interconnection. Just as in MMOs, in Skyrim you are an errand boy the moment you step outside the MQ/civil war.
Im sorry to break your bubble man, but sandboxes are single player MMOs. If you define "grinding" as "doing simple repetitive quests to level up and gain new items or more money", sandboxes
are grindfests. You can claim that you play to explore the world, but so could any MMO player. You can claim that you want to RP, but just like MMO players who can also claim the same, you cannot translate those into the game, so you have to do it "in your head".
Really, please, enlighten me. What gameplay, design or ingame element makes it so different, so unique, so non-MMOish. Because to me, when I look at what RPGs achieve nowdays in term of story depth, character/personality developpement and gameplay narrative... Skyrim is absolutely nothing like that.
EDIT: I think a lot of the disapointment comes from the fact that a lot of us have come to expect a lot in terms of story developpement when we see the lable "RPG". Skyrim is Morrowind with better graphics. In any other department, this is still a 2002 game, and those of us who are not die-hard fans of the TES series have come to expect more out of these games. You can argue all you want that the technology was limited, but the simple fact of it is that it isnt. There was simply a design decision taken to allocate funding to graphics instead of gameplay and narrative/storyline developpement.