I would argue that the Witcher 3 is not an RPG but an action game with rpg elements.
And I would vigorously disagree. But ultimately what matters is that none of us has copyrights over the term RPG, and, as @Madscientist says very well, the definitions don't matter so much as whether we enjoy a particular game or not. I love the "RPG" genre almost exclusively for my video gaming preferences. Hard to argue Ps:T is not an RPG. And yet, I don't care much for Ps:T and personally view it as an overrated game. We all have our weirdnesses and our peculiarities.
