Of course players assist in creating the sense of immersion. Playing a single session with bored, unengaged and otherwise disinterested players should be enough to prove that.No, a player's job is to immerse themselves in the world and stay there, not facilitate the immersion.
The player's input is still required to bring the world to life. Therefore, they are necessary 'partners in Creation' (sorry to keep using that phrase, I really like it, I think it's from Judaism).They are only responsible for their characters in the world. The world itself is going on around the pcs. The pcs can interact with it, and change functions of it, but its up to the dm to insure those changed functions fit in with the rest of the world.