Keaton has new fans because of being Vulture in MCU Spider-Man, so there may be some younger people who are interested. But honestly I suspect WB doesn’t care if Flash bombs, it’s job is to do continuity clean up and establish the Multiverse so they can move on from Snyder. Flopping will mean they dump Ezra but Keaton can still be used to prop up other peoples movies like Batgirl. That is what they’re really interested in.