In a way, DOOMSDAY CLOCK has *already* "fixed" continuity, insofar as we now have a viable in-comic explanation for Golden Age, Silver/Bronze Age, Post-COIE, New 52, and present day Superman that (more or less) works. Moreover, the JSA is coming back in a somewhat familiar form, though that seems to be happening as much through Snyder's JUSTICE LEAGUE as it is DOOMSDAY CLOCK.
Buried Alien (The Fastest Post Alive!)