In a lot of videogames, especially fantasy and sci-fi guff, you’re generally placed in a situation where killing one particular thing, or group of people, or monsters, or whatever, will fix all the problems in the world. Which is just as well, because you’re also usually playing as a character who’s proper good at killing things and has no other means of affecting the world around them anyway.
I know you all like your BioWare games with their big conversations and choices and that, but you’re still fighting the bloody Reapers or the Darkspawn, aren’t you? Christ, even a game as phenomenally smart and museum-worthy as Dark Souls has you attempting to sort the entire world out (or condemn it) by fighting and killing a crusty old god at the end. Even though it's ambiguous as to which ending is the 'good' one (if any), the fulcrum upon which everything rests is you having a good old ruck.
The Witcher 3 takes a bold half-step towards actually being a bit smart about this. You're playing as a man who spent half his life training to hunt monsters, and that is literally all he's good for. In most other games, where killing monsters magically solves everything, that makes him your archetypal hero. Here, he's just a guy who's good at his job.
While you do solve a lot of problems through the investigation and, usually, slaughter of monsters, the overarching problem in the The Witcher 3 is that of the ongoing war between Temeria and Nilfgaard. The latter has just invaded the former, causing a whole range of problems that are simply beyond the grasp of one handsome lad with a sword and some potions. Wander through any of the game's villages and you'll see people sobbing openly in the streets, many of them left destitute by the war. Famine is rife, and there's a fair chance that the folk you meet have witnessed the slaughter and/or rape of their loved ones at the hands of the invading soldiers. But we're playing as Geralt of bloody Rivia! He's the main character, in a videogame, so he's going to fix everything, surely?
Well, nah. He's good at killing monsters, which in many games would be enough. Here, it means he can marginally improve the lot of the few people whose lives are made even worse by the harassment of a restless spirit or a werewolf. But he can't sort out the food shortage, he can't take undo or prevent the horrific atrocities committed by the Nilfgaardians, and he can't teach the city-dwellers that becoming a howling pack of mad racists isn't really the way forward.
The Witcher 3 deconstructs the monster-slaying fantasy hero myth a little, suggesting that when faced with many of the real-life horrors of conflict, one man being incredibly skilled at killing baddies is only ever going to make the slightest push against the fucking tidal wave of misery. Geralt might be a hero, but in The Witcher 3's world he's of no more genuine use than a decent chef.