To me 5G and Doomsday Clock kind of feel like a natural progression of Rebirth and the New 52 in a way. Rebirth was where everything that you once loved came back, all the continuity and characters. But a natural question out of that is how does that work when a lot of characters are just different from how they originally were thanks to the New 52 and having to naturally progress out of that with Rebirth, ex. Ted Kord Alive, Batgirl walking, Black Canary a rock star/spy/single, Wallace West being alive and etc. So now that we've put back the continuity we now have to put the timeline back in such a way that it works for the continuity to have occurred. So in a sense it makes sense that to me characters are gonna get aged to go, hey our stories chronologically make sense. At least to an extent anyway, but hey we can always blame Crisis on Infinite Earths. Because no matter how good the story was or how influential it is, it kind of started this mess of confusion with characters from different times and earths now all living together in one continuity.