Originally Posted by
Hitei
With Legion on the drawing board and the Void not far off in narrative preparation, they saw a chance to reset as part of this bookend -> new chapter progression. In an effort to turn back their mistakes, they introduced the First Ones as a mysterious, unknowable group of beings, who unlike the Titans, don't have an appearance, and don't speak our language, and don't have minions who are just big humans. Then they needed, on paper, the slight hint of a motive for these new mysterious god-beings, so they introduced "the Seventh".
That way, when they move into the next chapter, they've effectively reset. We know everything there is to know about the Titans and Legion, and Old Gods, and the Void is simplistic, but in the next era they'll have the First Ones and Seventh to keep far off in the distance as a mysterious thing we don't really know much about. The new version of the Titans and the new version of the Old Gods.