Just because no game has successfully awakened the Old Ones yet doesn't mean it's not going to happen.
With respect to the issue of the cerebral path that the protagonist takes, hunting down clues and piecing together information, this describes the pure adventure game (Myst-style, not Zelda) perfectly.
But to create the slow realization of the apocalypse...
You have to gradually realize that you, personally, are responsible for the end of the world. I think that means that it has to be an MMO (for persistence, can't just restart into a new, undestroyed game world) where the final endgame for one very powerful character is to bring down the game server, to make it unplayable.
Now, to prevent the *server* from simply resetting once the game is over. You can't, really, so you have to make the initial state of the game as boring as possible. Given Game 3.0, I think that this could be doable. A thin baseline of meta-rules would allow players to gradually build up a complex, rich, well-developed world, something really worth keeping and missing; and eventually to unmake it forever. That is the apocalypse.
And, yes, I do expect a lot of players to react to the realization that their lovingly crafted world is doomed with something akin, if not to insanity, then at least to raw unreason and panic. Compare Corrupted Blood: people react to catastrophe as they would in real life. The Cthulhu game waiting to be made is a nomic with a tragic flaw.
Just like real life.