Do you think that “knowing what’s going to happen” is the issue? I mean, I can read Pride and Prejudice with enjoyment, or Kim, or Gaudy Night, or The Lord of the Rings, or Atlas Shrugged, or Courtship Rite, or The Moon Is a Harsh Mistress, despite having read each of them previously more than once and knowing how the story goes. There doesn’t seem to be a “find out what happens” after three or four readings. Yet it seems to me that you do read novels that you like more than once.
I do feel that in RPGs, player characters have, and ought to have, agency. And a predecided plot makes that unattainable and the game no fun. But I don’t know if the problem is one of knowing; it seems to me that something else may be the issue.