I'll be honest I didn't read your post in it's entirety so ignore my comments and call me ignorant if you wish but I'll go on anyway. I think I understand what you are saying and I completely disagree with you. The car metaphor you used is just plain wrong. Open world's and good combat systems are two of my most important factors when determining how good an RPG is. On the other hand the seats in cars are of almost no importance at all so to group the decisions together is nonsensical. I understand that we may differ in opinion there and you might value other aspects of a game more but that is certainly how I see it. Hell one of the best things about M&B and the reason I loved the first couple of games was it's relatively open world and combat system. As far as I'm concerned there is a lot of choice in Skyrim, clearly it is limited as are many games in the sense that to make a 100% choice based game would be near impossible and just not viable.
My reaction to your post my be slightly warped however as I am very against genres in general. I don't like grouping games (or movies or books) and then judging them in their groups. Perhaps you are right and Skyrim shouldn't be classified as an RPG but it is. So in my opinion it is an RPG and is a good game, and is therefore a good RPG regardless of it's contents.
I'll disagree with you right from the bat here.
Combat systems and open worlds are not the defining factors in an RPG.
If so, BF3 scores well as an RPG as it has large open levels, and a good combat system. Nevermind that its not an RPG at all.
What matters in RPGs is not the combat system - Most certainly not the random chance to kill someone within that combat system - nor the open world element. As was stated earlier, in an RP you can roleplay a guard guarding a castle, you aren't going to get a lot of open world experience out of that. You'll get basically none. Combat is likewise not massively important - though it has been given more emphasis recently - as it should be 100% possible to make it through a lot of an RP experience without fighting. Sneaking, hiring thugs, talking and learning about what's ahead, finding out where traps are and luring your enemies onto them - all alternative ways to get away from combat.
What are the important parts of an RPG are the characters and the world, the players ability within that world and the playing of a role, not being that role.
Skyrim succeeds in the latter, but fails in the former, and here is why:
In Skyrim, the player can do anything they want really. They are free to play as they will. The main problem with this, however, is that nothing responds to that. What is the point in levelling up to max level? There is none. Honestly, it just makes the game harder due to level scaling. Why complete the thieves guild questline? So Brynjolf will stop talking to you? That's about it, otherwise its simply that you get loot and money. Why do anything in the world, when all that will happen is a guard will have one more random line of dialogue, that they MIGHT say based off a random answer.
The world does not respond to you. A very popular example is the Companions. Join them later in the game, after you have killed Alduin. After everyone knows you are Dovahkiin. After you've become Archmage of the College of Winterhold, assassinated the Emperor, finished the thieves guild. Do everything else that the game has to offer - absolutely everything - then talk to the companions for the first time. This is what will be said somewhere in the conversation: "Are you sure you want to let him join? I've never even heard of him!".
That is poor, and just lazy really. All that would have been needed is a few extra voice files and some if/then/elses and variables, and he could have acknowledged who you were. "Are you sure you want to let him join? He's a mage, not a warrior!".
Likewise, I greatly doubt that the College of Winterhold is actually for mages my warrior went in there, and completed the entire story with his sword. No-one asked "Why aren't you using magic?", and when fighting with the companions, using magic only, no-one thought it was dishonerable, and that I should fight like a Nord should. The world didn't care. Everything in Skyrim is there for the express purpose of you satisfying your want to kill something in some exotic way. The choices mean bugger all, since very little happens to deal with them. You can kill an entire towns worth of guards, pay your way out of it or get sent to jail, and you know what? No-one cares.
Playing a role not being a role may sound odd, but it is important. In an RPG, you should play your role, and not be able to be your role. An example if you will:
In Skyrim, I am able to aim my bow and kill a giant at level 1.
What should happen is that I tell my character to aim their bow, and their aim decides whether they hit or miss.
In Skyrim, I override my character's skill with MY skill, making the role become me instead of me become the role. My character could be the worst shot in all of Tamriel, level 1 archery and unable to hit that tree that the bow is right next to, but I can override that and become the best bowman in Tamriel in an instant.
This should not be possible. It forces the role to play the player, instead of the player play the role. It is why no RPG should ever let you take control of aim or any other combat related action. If you do, you are not role playing, you are making that role play you (In Soviet Russia...). The pickpocket system does this correct. Combat systems here do it incorrect. Lockpicking does it incorrect, ect.
Good Combat (Proper RPG style system, which most don't think of as a 'Good' system, hence my disagreement with you right from the start) and an Open world are not so important to an RPG. The world itself, and how it reacts to you, and whether you play a role or that role plays you, are all far more important, and some of the defining features of an RPG. For having fun in an RPG Combat might be important, as might Open-Worldeness for some, but that is not important for it being an RPG.