Once upon a time in other words, before September 2011 the DC Universe had history. It wasn't that the stories were part of a larger narrative that had been published for decades, although there was that, but that characters in the DCU had at least the illusion of growth and aging.
The Justice Society had fought in World War II. New characters took on the name and legacy of their predecessors, and had to deal with the weight and responsibility that brought.
There was, at the very least, the idea of things being impermanent and change being part of the world, because you knew that Hal Jordan was Earth's second Green Lantern, or that Dick Grayson had not only retired as Robin, but that he'd gone on to grow into the mantle of his mentor.
Now, all of that has been wiped away, and the DCU's superheroic history only stretches back for five years or so. Sure, that might make the stories easier to sell as jumping on points for new readers, but there's a lot that's been lost in the process that didn't need to be.