They did that. It was called Earth One.-A set of worlds where each hero are the only heroes of their world. Superman is the only hero in his world. Flash is the only hero in his world. Wonder Woman is the only hero in hers. Then some event brings them together or cause them to switch the others worlds. Awkward interactions because they don't have the same history with each other and each hero notes the difference the other made in their respective worlds. Maybe shared universes are more chaotic and dangerous than singular worlds but on singular worlds, the heroes are more worried about would happen if they can't handle a threat or who would protect the world after they die.
-The Switcheroo verse where we switch the genre of each heroes. Superman is an actual Demi God sent to earth by Ra for his protection. Batman is a mystic hero who uses a magic cape to fight crime. Wonder Woman and the Amazons are actually meta humans who learned how to activate the genes unlimited potential with the Greek Gods being like Saiyans; humans who reached their god like potential. Zatanna is an inventor who uses gadgets to make it seem like she's doing magic. Flash gets his powers from Hermes while Green Lantern gets his from Demeter. Aquaman resembles the creature from the Lagoon and him plus the Atlanteans are water based aliens who settled down on the ocean floor millions of years ago.