Here is my personal semi-subjective view on why Skyrim's roleplaying mechanics always falls short for me.
Below is my very subjective semi-rant on the Skyrim DLC states & quick perspective on what I have always personally deemed of Skyrim's roleplaying mechanics:
The plot and everything left hanging has never bothered me







Now I will review what I have just stated above and hopefully put a lot of things into user-perspective:
Cosmetic roleplay - To put it in a somewhat objective sense, no Skyrim does not lack roleplay

unconstrained -The only thing now that would hinder you from advancing your perk progression are the decision of the player to acquire a perk based on it's usability/viability/cosmetic function, and the previous prerequisites of that perk (which is 100% of the time is another perk

unconstrained - When you put it again in perspective, what does unconstrained mean? Less bounderies right? = Character development unchained. The more unconstratined character development is, the more it will lack specialization & solidness, which I find true for Skyrim. So as to why there are may debates on why _______ is overpowered/underpowered.
unconstrained - On chargen again with the removal of classes and major racial diversity, yes a lot were done in a unique broader but it had some major impacts on roleplaying value. There was nothing to give your character a backstory for chargen at Helgen except for some 5-10 differences in weapon proficiencies and racial powers - it was the equivalent of being a "newborn" as an advlt character who should've had unique traits. A race itself is not enough to suffice for backstory - this is what I mean by "cosmetic roleplay". Bethesda should've also deviated from the small gap between vital racial stats, ie. Orsimers with 200 health and Altmers with 250 magicka wouldn't have had hurt for compensation of removal of something to give you backstory roleplay value.
unconstrained - No faction diversity. No consequences and conflicts. If you complete every faction questline your character may feel like having a multiple personality disorder syndrome, that once valorous knight of yours has turned into a kleptomaniac and your precious roleplaying intent for him has been lost to greed. The previous titles of the main series had at least some diversity but still with minor consequences ie. Morrowind had some halted quest progression because you were a member of another faction and disposition impacts on opposing factions you have joined and Oblivion had conflicting quests. Though still minor conflicts and all other factions were still open for questline completion it would've been great to really see Bethesda deviated with Skyrim even more by bringing the "impact-oriented open world rpg" into play.
Do everything you want you're Dragonborn - Here is where all is forgiven and lost. This is why I guess it was a challenge for Bethesda to fit everything in from some of the stuff I mentioned above (which is about 0.8% of what could've been done) this is why Skyrim turned to 70% open world and 30% roleplaying game. The dire need for a new Dragonborn has immersed us in the game in a different type of way that roleplaying and our character backstory didn't seem to matter much.
Dragonborn - I think there is a subliminal intent of Bethesda that the Dragonborn should have no need for consequences. Which is agreeable to some extent.
Dragonborn - Skyrim is epic in it's own unique open world way.
Dragonborn - Again all is forgiven and well.
This just lead back to the casualization debate and I don't want to go there - I tend to think there is no such thing as "casual games" or "casual gaming", there is just preference and the state of mind.
Casual games - The whole "casualization" in gaming debate is really a shallow point to argue & debate upon whether a game is tagged as a "casual game" or has been "casualized" is highly subjective as to calling Skyrim a medieval GTA game. There is just realizing that your own knowledge & subjective perception of a game will override any other one's.
Skyrim's mechanics - With every new title to the main series of the Elder Scrolls games Bethesda deviates from the previous ones. I can only hope that the next one will be far off from Skyrim. I personally do not want a "Skyrim II".
Skyrim II - No please no.
Skyrim II - Out of all the main series I would have to say the best transition would be from Daggerfall -> Morrowind. Morrowind had 50% open world, 50% old-school rpg 50% simulation, & 50% of what Daggerfall and Skyrim was well Skyrim..
I just wish the next ES game would have this balance, I want to be able to wipe out & destroy enemy factions (gimme plots full of depth, intrugue, and conflict), really roleplay my heart out, a dynamic and impact-oriented world, and a game that rewarded you in the most unique and creative ways.