You see it all around comics within the last 15 years. They're either doing shared mantels or outright replacements of characters that were created in the 20th century. DC was even the first to blaze the trail with the replacing of GL and Flash in the Silver age, and then again in the 80s.
This is just the first time they've tried to go for the big whale. And it's not like back in the late 70s or even mid 2000s. This is at a point where the Ls to Clark's name have piled up, Marvel is blazing a trail forward, and DC continues to look like "your granddad's heroes". It's a perfect storm.
Remember how back in Post-Crisis one of the first things they did to shuffle Hal off was gray up his hair and really treat him as out of his prime? Before you'd have to hold DC at gunpoint to get them to treat Clark, Bruce, and Diana as anything more than being in their late 20s early 30s. And getting them married was always a bitter pill for them.
Now Aquaman has a kid, Bruce was almost married, Superman has a kid, all that history is back so you can't pretend they're all 29 anymore, and now the only live action version of regular Clark around is one where he's married with two teenage boys and decades of being a hero.
It was a mass Hal Jordan-ing of the older heroes. And now it's a more subtle version of that. Keaton being the main universe Batman speaks for itself.