>>/50823/
That depends on definition of genre, and the mix of them too.
Rpg, adventure, action are frequently mixed, but each has own characteristics. RPG also used quite loosely, technically anything can be role-playing, like I can play the role of Duke Nukem... They also call something rpg because characters are assigned stats, which personally I think is stupid, and a bastardization of the pen and paper role playing games; but that's what computers do, counting numbers.
I think interaction with NPCs is a huge part of RPGs, large part of the role how you do it. Ofc there can be settings and stories where the player or players are very isolated and the interaction with the world will miss the element of dealing with people in other way than killing them, or dealing with them at all.
I can't judge Witcher 2 for I have not played it.