Not at all , a lot of people collect it's just when it comes to Toys it's perceived differently to older people for some reason. I really fail to see the difference collecting, Buttons, Stamps, China, Spoons, Shoes, Makeup, ect collecting is collecting no matter what it is.
I'm in my early 20's and I collect Anime Figures, Manga, Games, Plushies and a few other misc things (I wouldn't say my collection is huge compared to some people but its a nice size) but overall I enjoy it and it makes me happy. The only thing that would make this hobby more fun is if I had someone to share it with irl but other than that I love it. I admit in the back of my head it sometimes slips "maybe I'm to old or I should stop" but then I thought about it define "being an adult?" because even partying can be seen as immature.
I think we feel this way because the gen. before us didn't have as much access to the internet so it wasn't as known about people and collecting but turns out millions of people collect stuff!