I was actually watching an interview with Neil DeGrasse Tyson recently and it’s not inconceivable that our universe is only one in a vast multiverse. So who knows, just because people don’t think something is real doesn’t mean it’s not (maybe not in our universe but perhaps in a different universe the entire DC mythology is actually playing out), just as people may think something is real and it isn’t.
I also think that mythological entities have been shown to be local, while some areas did account for the major pantheon of sat greek mythologies, a local group in a different area may have also had mythology that was local to them as well. Maybe the b-d listers. We also know that many mythological tales have been lost to time. Perhaps 2000 years from now Superman, Batman, WW and other stories and characters will be remembered, but GL Corps, BOP, and Wally West, and others will be lost to time.
Reboots/Crisis events, Golden Age vs Silver Age. That is the interesting thing about comics. There are multiple Pantheons, think Greek, Roman and Norse and there are many more over the time and location). Kinda makes sense. Hades may be the lord of the underworld in one and we have a gender swap with Hela in another. They both serve the same or very similar function. (Maybe that’s why changing an existing characters gender, ethnicity, orientation doesn’t bother me.)