The primary source of the "Titans first" story is the Tribunal of Ages, which as a Titan machine is vulnerable to "unreliable narrator" syndrome. Or in essence, everything it said was Titan propaganda.

In particular:

Brann Bronzebeard yells: Query? What do you think I’m here for? Tea and biscuits? Spill the beans already! Tell me how that dwarfs came to be! And start at the beginning!
Abedneum yells: Accessing prehistoric data. Retrieved. In the beginning Earthen were created to-
Brann Bronzebeard yells: Right, right! I know that the Earthen were made of stone to shape the deep reaches of the world but what about the anomalies? Matrix non-stabilizing and whatnot.
Abedneum yells: Accessing. In the early stages of its development cycle Azeroth suffered infection by parasitic, necrophotic symbiotes.
Brann Bronzebeard yells: Necro-what? Speak bloody common will ya?
Abedneum yells: Designation: Old Gods. Old Gods rendered all systems, including Earthen defenseless in order to facilitate assimilation. This matrix destabilization has been termed the Curse of Flesh. Effects of destabilization increased over time.