Who do you think makes professional quality fanart and fanfic? People who've been practicing it for ten, fifteen, twenty years!

Or even people who've been practicing it for thirty, forty or fifty!!!!!

example: Diane Duane. Currently in her seventies. Star Trek fangirl since the original run. Goddess-level Ascended Fan who has created official tie-in works in more forms of media than pretty much anyone else alive, possibly even Rodenberry himself because they didn't have audiobooks or video games when he was with us. Writer of Spock's World, The Wounded Sky, Doctor's Orders in TOS. Co-writer of TNG script Where no one has gone before, and writer of the tie-in novel Dark Mirror among others. Writer of a half-dozen Star Trek Comics. She has adapted her own work for audio, has written for the Star Trek manga series, has written short Trek fiction for anthologies, and plotted and wrote the video game Star Trek: the Kobayashi Alternative.

In other fandoms, she was a personal friend of Terry Pratchett himself. As a scriptwriter, she's also worked in fandoms like Scooby-Doo, Transformers, My Little Pony, Gargoyles, Batman: The Animated Series, Spiderman: Unlimited (and a trilogy of tie-in novels still in print) and Barbie: Fairytopia. ...And that's just cherry-picking her imdb page.

While she can't give out specific details due to Obvious Reasons, she's still active in the Sherlock BBC fandom - and there's a specific subset of her fans who love guessing which of the legendary fanfics might be her work (I am not one of them, BTW, as it is None Of My Business. I'm old-school that way).

Fandom is not for teenagers. Fandom is for everyone of good heart and enthusiasm for a good (or even bad! No judgement!) story.