That's a pretty broad generalization there. The new suit, to my knowledge, wasn't created by 'modern' fans. I guess you're assuming that we've influenced its formation to some degree though. That I don't know for sure. I can only speak for myself. Although, I'm fond of the Superman character, I've never been overly thrilled with the
entire costume -- even as a child. I think you can be a fan of something without supporting every single aspect of it -- kind of like a favorite rock album with one or two songs you aren't crazy about. And with comics, there's
so much you can be drawn to even if you're not into a particular character's costume design from inception. Of course, with you, it seems to be all or nothing.
Your viewpoint is interesting, but you assume too much. It's certainly quite possible that 'modernizing superheroes' has broadened their appeal to mainstream audiences
on at least some level. In my opinion, it has. If you take away all the color and theatrics from comics, they're often just well written mystery or action tales. Likewise, when you make a superhero movie of substance (e.g., Xmen: First Class, The Dark Knight), I think you're going to have a certain number of mainstream audience types (non fanboys/fangirls) who are willing to give the comics a try even if it wasn't initially their cup of tea. I know one thing for sure: Comic-to-film adaptations are a lot more popular nowadays than they were when I was growing up.