9. Some Proper Connective Tissue
Along with the bombshell that Keaton had entered negotiations with Warner Bros. to reprise his role as arguably the best-ever version of Bruce Wayne came the news that the actor was being lined up to star in multiple DCEU movies, not just The Flash.
As a veteran actor whose most famous ties to the comic book genre saw him clad head-to-toe in black, speculation almost instantly started that the studio were keen to use Keaton as their version of Nick Fury, a beloved exposition machine that can further the connective tissue between various standalone franchises without being the focal point of any of them.
The DCEU is technically all connected, but it has never relied too heavily on the sort of crossovers that are the bread and butter of the MCU, with most of the references reduced to brief Easter Eggs.
Having Keaton's Bruce Wayne act as Barry Allen's mentor is a smart first step, and nobody would bat an eyelid if he went on to tell Aquaman to cut back on the whiskey or crack a joke about how Wonder Woman has aged much better than he is.