Fan art is still legit art.How do you produce original content if you're just copying?
Sure, but I mean specifically looking at a picture and copying it down. My own style is incorporated into the piece, but it's not really mine. It's just my take on someone else's piece. I'm certainly no expert on what would qualify as "art", but I wouldn't be impressed with someone else's version of The Mona Lisa, for example. Someone creating their own Superman comic, while copying the style of Superman, would be creating original content. They'd just be using an established character. I don't know if I explained that clearly, but I hope you understand what I mean. If not, I'm happy to try again!
You just described a lot of fan art. These people you see who make original art almost always start with fan art of some kind. Maybe they were the 10yo drawing perfect Bart Simpson. Today they are the kid on tumblr wowing their favorite webcomic artist with fan art in their own style. Tomorrow they'll have their own story.