I was just disputing what you said about the 70s having WW2 nostalgia for the JSA. PRE-Crisis on Infinite Earths, in issues published in the 60s, Jay Garrick was established in his first Silver Age appearance as a WW2 superhero. It wasn't WW2 JSA "nostalgia" in the 70s, it was straight from the reintroduction of the golden age Flash. I never even hinted that I'd want the JLA members to be from the 50s/60s, I was just saying that, even in the 60s, they connected the Golden age JSAers with WW2.
WW2 is the core of the group. They came together because of WW2 (and yes, that was a retcon, but one that stayed in continuity for most of the team's time outside of the Golden Age). They fought through the war as both the JSA and All star Squadron. Also, the 70s All-Star revival was all about a group of World War 2 heroes and the younger people trying to join the legendary team. Why the hell does it matter if they're 90 or 50? Hell, the 70s All-Star Revival shares a lot of the same people as Geoff Johns run anyway, at least when it comes to the old JSAers. Being 90 slows very few of the living JSAers down.
Keeping their WW2 history gives them a legacy, and one that has been part of the group in every incarnation since they came back in the Silver Age. Yeah, some members are dead. So what? There is still a Doctor Midnite, a Mister Terriffic, and a Sandman. Is it super important that they be the originals? Some members died heroically, some died of old age. Some age slower, or got deaged, or don't actually age because they're sentient energy now. Some got replaced by their children or others. Its all part of what makes the JSA cool. There are a lot of other factors in that, obviously. But, in the end, they're a WW2 founded team. They've been associated with that basically forever. From actually fighting Nazis in Golden age stories, to 60s stories where it was established they fought in WW2, to the 70s where it was also established and they even fought WW2 villains. They're connected to the war. That's not even remotely all they are, its just a part. But its a noticeable and important part.