It’s interesting though — the culture of shame surrounding adult women and fandom. Even within fandom it’s heavily internalized: unsurprisingly, mind, given that fandom is largely comprised by young girls and, unfortunately, our culture runs on ensuring young girls internalize *all* messages no matter how toxic. But here’s another way of thinking about it.
Sports is a fandom. It requires zealous attention to “seasons,” knowledge of details considered obscure to those not involved in that fandom, unbelievable amounts of merchandise, and even “fanfic” in the form of fantasy teams. But this is a masculine-coded fandom. And as such, it’s encouraged - built into our economy! Have you *seen* Dish network’s “ultimate fan” advertisements, which literally base selling of a product around the normalization of all consuming (male) obsession? Or the very existence of sports bars, built around the link between fans and community enjoyment and analysis. Sport fandom is so ingrained in our culture that major events are treated like holidays (my gym closes for the Super Bowl) — and can you imagine being laughed at for admitting you didn’t know the difference between Supernatural and The X Files the way you might if you admit you don’t know the rules of football vs baseball, or basketball?
"Fandom" is not childish but we live in a culture that commodified women’s time in such away that their hobbies have to be "frivolous," because "mature" women’s interests are supposed to be caretaking, via marriage, children, and the lives of those within an imagined (generally nuclear) family unit: things that allow others to continue their own special interests, while leaving women without a space of their own.
So think about what you’re actually saying when you call someone “too old” for fandom. Because you’re suggesting they are “too old” for a consuming hobby, and I challenge you to answer — what do you think they should be doing instead?
