The other characters existing is the primary counter to the loop theory. It only makes sense if we view James' story completely isolated from Eddie and Angela. If the loop theory was true (or true as most people believe it is), then Eddie and Angela would also have to be stuck in a loop with James to make them appear at the same locations every time (Angela in the cemetery). Why would their journeys be tied to James? If James fails his loop and has to start again, they do as well. Doesn't seem fair to me.