I'm fine with it, if it works. The old-school Fallout games never held my attention. However, Fallout 3 is one of my favorite games of all time. I love the FPS/RPG set in the Fallout universe.
I guess my point there, is that if there is an established lore behind a game, there is no reason to make it stick to the same genre. Take a franchise, do you want to with it, and see what works and what doesn't. The world the devs create shouldn't rely on a specific genre.