KISS was the ultimate expression of 70s rock hype. They took parts of glam, parts of bubblegum pop, parts of comics and horror movies(their look was very influenced by 70s Marvel Comics--crossed with David Bowie--which made this a good fit), used the same theatrical arena-rock approach that lives to this day in U2, stole liberally from Alice Cooper while getting rid of the darker and rougher nature of his music(though he too was a "brand") and made their concerts basically circuses. It was rock vaudeville. It was an image, marketing, a brand, and the music was deliberately designed to appeal to the LCD. People Cheap Trick or Aerosmith were too smart for. You couldn't have a comic book, TV specials, and toys of Cheap Trick. This was carefully and cleverly packaged.
That's just an observation, not necessarily a criticism. They were very, very good at it. But there's a reason most can't recall a song of theirs from the makeup period besides "Rock and Roll All Night" or maybe "Beth." Neither of which is exactly heavy or dark. I will confess a fondness for the thudding, brilliant dumbness of "I Love It Loud," though. There is such a thing as good 70s hard-pop, and that'd be an example.
They were the ne plus ultra of what was called and is called "Corporate Rock." Amusingly, though they cultivated this dark look, and did stunts like the fake-blood thing in concert(or fire-eating, again, a circus or carnival thing), but their competition was not Alice Cooper(who, granted, was super-successful in the 70s) so much as ABBA.