I mildly dislike it, because it nudges all characters towards one of the three archetypes and makes it harder to craft a character that breaks free of all of them. I also don't really see a point to specialization.
I espouse the opposite position. Oblivion's endgame characters are god-like enough to begin with, at least specialization helps characters focus on one major skillset. I mean, its a single player game, play it however you want, but FWIW I don't hate the warrior/mage/theif fantasy archetype system just because its established. Only my opinion, but if you want to make a stealthy warrior-mage, and not suffer low stats and other limitations, you might as well just open console and 'tgm' yourself, but again, you can play however you want.
Fallout 3 didn't really have anything too limit player character omnipotence, and by say level 10 it was hard not to have a character that was great at
everything. I'm sure there were mods to fix that, but I played F3 on the Xbox, so to enjoy the game 'my way' I had to play my characters by my own rules: my main character used melee weapons (the tenderizer specifically for the most part) for 90% of all combat (I'd say the rest was 8% grenades and 2% Blackhawk for those hard-to-reach places). Fable II was (as is always the case) even worse; by the end of that game the PC was highly proficient in at least 2 of the 3 archetypes because the game gave out tonnes of XP, and the combat gameplay generally required strenght and magic skills or strength and speed/firearm skills.
In TES4's execution of specilizations, some of the categorizations were goofy, as people have pointed out. They seemed to hammer some things into 'stealth' skills just for the sake of getting them in one of the big three.
But the general idea of a game rule mechanic that guides characters towards the mighty glacier warrior / the glass cannon caster / the backstab rogue archetypes, and forces compromises to be incurred by those looking to blend any combination of classes is a good thing in my book.
I like my classic fantasy tropes.