How was that any different than Sgt Fury being part of the "superhero" universe? Or Doctor Strange for that matter. Horror has been a part of superhero comics since superheroes began.With vampires, werewolves and mad scientists among the earliest villains. Even Marvel's western, teen and romance titles/characters are part of the "superhero" universe.Quoted for truth, but hacks being hacks cannot stop themselves from hack concepts.
Because writers should never step outside the box. That way we can accuse them of being uncreative shills.
I've watched the crew of the Enterprise explore countless strange new worlds, battle the Klingons, battle the Romulans and so on in countless episodes, novels, comics and video games. I think crossovers with other universes is ultimately good for my enjoyment and good for the overall brand.
ST and superheroes are different animals, catering to equally different plotting demands. This is as silly and out of place as the 1970s, when Marvel shoehorned a bunch of horror characters (Tomb of Dracula, Werewolf By Night, The Monster of Frankenstein, etc.) into their superhero universe with less than spectacular, or even sensible results.