Good characters and good stories are timeless and ageless. I mean look at Harry Potter. Originally it was a "kid" book about a boy going to magic school but now there are college courses about it. Same with ATLA. You're never too old for a good story.
Never. My parents like it. Also I'm in a high school and one दिन in art class my friend and I startd talking about Avatar. Soon half the class had surrounded our तालिका, टेबल and wanted to talk about Avatar.
i watched it when i was 14 im almost 17 and i do still watch it im waiting for the अगला one to come out,HEY your never too old to watch cartoons,in fact my mom watches it with me.