But do you see where the appeal of the fantasy can sometimes lie in imagining that its happening to people like you and me, in a world enough like our own that that the fantastic elements stand out more? Look at 'Salem's Lot by Stephen King. There are absolutely no new ideas regarding vampires in that book, but what makes it work is that King makes his small town and its people feel utterly believable and lived-in, so that when the unnatural elements intrude, they're all the scarier for taking place in believable, realistic setting where they don't belong.
For a single story, sure. But for an ongoing series, as I said, it limits the long-term storytelling possibilities if the impact of the extraordinary phenomena always has to be reined in or quashed or negated. Good writing in any genre is about actions and consequences. It's the consequences of a story's events that give it stakes and meaning. An unwillingness to alter the status quo of a show's world imposes an artificial limit on the potential consequences of an event, and that weakens the storytelling.
This isn't just true of stories set in the present, either. Look at
Deep Space Nine's first season. In the span of just a few episodes, we were introduced to the technology to create adult clones within days ("A Man Alone"), the technology to heal any disease and even death ("Battle Lines"), and the technology to transfer a dead person's consciousness into a new body ("The Passenger"). Collectively, those technologies should've revolutionized civilization and eliminated death forever. Only one of the three, the nanites in "Battle Lines," was given a limitation that prevented its wider use, but that limitation was artificially imposed and could've been overcome with further study. The other two were given no limitations precluding their continued use. But they were all ignored thereafter, their consequences undeveloped, and that made the stories less plausible.
Same with superheroes. A guy leaping over tall buildings in a single bound is more jaw-dropping if it takes place in downtown Metropolis than in some exotic transhuman alternate world where such feats are commonplace. It's about evoking the "sense of wonder" effect of the awesome and the miraculous.
But it's easier to believe in a superpower or sci-fi phenomenon if it has the transformative consequences on society that one would expect it to have, rather than having society just artificially remain stagnant despite the existence of these extraordinary aspects. It's the
Reed Richards is Useless problem.
After all, your analogy here doesn't really work. Most comic-book universes are ones where the existence of superpowered beings and extraordinary phenomena are commonplace. Much of the fun of the Marvel and DC universes is how ubiquitous all these wild, bizarre things are and how normalized they've become in everyday life. These are worlds where the existence of aliens is common knowledge, where the ancient Amazons or Atlanteans have an ambassador to the UN, where the bizarre and extraordinary is part of everyday life. (Have you read the
Unbeatable Squirrel Girl issue where Doreen tries internet dating and ends up on a date with a guy who turns out to be a "superhero truther," convinced that all superheroes, villains, gods, monsters, and the like are government propaganda and false-flag operations? In that world, it's the
disbelief in the extraordinary that puts one out of touch with reality.)
So it's not the same as the sort of series we're talking about where the extraordinary is a secret from the general public or is considered a hoax, the kind of story that allows us to pretend it's taking place out of sight in the real world. There used to be a number of superhero TV shows like that -- the bionic shows,
The Incredible Hulk,
The Greatest American Hero, early
Smallville, Birds of Prey -- but there have been plenty of others where the heroes were publicly known, like
Batman, the various Superman series,
Wonder Woman, The Amazing Spider-Man, The Flash (1990),
Power Rangers (kinda hard to fight giant monsters in secret), and the like. And the "common knowledge" approach is used in most of the current superhero franchises -- X-Men, MCU, DCEU, Arrowverse,
Powers, Powerless (that's an interesting double bill), etc.
So I'm kind of lost by the equation of superhero fiction with "This is secretly going on in our world" fiction. Those two genres don't really overlap that often.
But that's just one approach to the material, that leans more heavily on the sf end of the spectrum. There's a whole rainbow out there and, to my mind, you can enjoy a story without having to believe that it could somehow conceivably happen someday.
Well, like I said, it doesn't have to be about science. It's about the internal believability of any fictional world, no matter how fanciful its laws. If it stands to reason that a given thing should have an impact on the world and it's artificially constrained from doing so, that's either a failure of believability or a missed storytelling opportunity. Because consequences and impact are
interesting.
After all, speculative fiction is "What if...?" literature. It's about asking "What if X happened?" and positing an answer. It's all about exploring the ramifications of an unreal premise. So when any work of speculative fiction -- whether it's SF, fantasy, horror, or anything in between -- poses a premise and chooses
not to explore its ramifications for fear of diverging from the real-world status quo, I see that as a missed opportunity.