I'm 13 and I still enjoy animated films. Unfortunately, since there aren't as many good animated TV shows these days, I don't watch them all that often. But there are certainly some good ones out there.
This stamp is now very outdated. Barely anyone calls cartoons "immature" nowadays. And anyone who does is immediately laughed at.
Way back in 2007 (when this stamp was uploaded) there was still a lingering stigma. But nowadays thanks to the exponential increase in nerd culture it's considered very normal to like cartoons, anime and family-friendly video games.
Back in 2007 if you admitted to liking Pokémon you'd be given weird looks. Now if you DON'T like Pokémon you're given weird looks.
Not only that but there are some cartoons that are SPECIFICALLY MEANT FOR ADULTS (Family Guy, Cleveland Show, American Dad, Happy Tree Friends (sorta; it's more just super bloody and gorey than dirty humor though))
That's true. Just because it's animated doesn't necessarily mean it's for kids - sometimes it's meant more for adults and teens, and sometimes it's made for kids but can be enjoyed by teens/adults just as much.