This is why most walking sims that descend from first-person shooters have been radical reimaginings taking years to produce, not merely removing enemies but crafting whole new environments, often with custom textures, objects, music, and narration: creating not just a new focus of interaction but an entirely different kind of world to support that focus.
This excerpt is very interesting as it explains that it is not as simple as you may think to turn a first-person shooter into a first-person walker game. In my own experiences playing both types of game I have noticed how much more detail goes into adventure and walking simulators compared to a fast-paced combat game.