Good question...
I suppose D&D was the original (or one of them) role-playing game...and the point there was that you could have whatever kind of character you wanted, in terms of personality and choices. Sure, there were things like strength and dexterity attributes, and classes...but those were more to formalise a framework around a shared world...
It's easy to see how games like skyrim and fallout fit in the RPG category - they're open world, you have a lot of freedom in where you can go, your playstyle, your appearance, how you interact with others...yes there's a main story, but you don't have to do it...or you can do it in various ways.
The division has elements of RPG - skills, customisation...and it's not on rails like bioshock infinite...but to me it seems more like an evolution of an FPS, since there is a certain lack of freedom...of course, in the PvP zone you could decide to hunt and backstab other players, so that's a "role" you've chosen for yourself.
I wonder about theme park MMORPGs - they have all of the customisation, emotes, outfits and everything...and they have massive worlds to play in...but realistically, a max level character wouldn't return to the beginner zones unless the game scales you (like GW2)...so it's more the illusion of freedom.
I guess the thing is, a computer game isn't going to be able to offer the same kind of freedom as a pen and paper RPG...there's always going to be rules and constraints of some kind...maybe the boundaries between FPS and RPG are so overlapping that they don't really meaningfully exist anymore...