Someone said that actually cartoons are for kids. It is the stupidest thing I have ever seen. That man was totally wrong (well, mostly). Let me explain. I am an adult and also love to watch some cartoons. From my perspective, it is a good way to spend your time. First of all, I learn English, so these cartoons help me with it. Also, good cartoons always leave you some mystery, deep interesting thoughts and there is always something that you need to understand after watching a cartoon. Well, films work in the same way.
But also there are a lot of bad cartoons that really can make you stupid, especially if you are a kid. They have no purpose to teach you, give you interesting and fascinating stories, etc. They are here just for one reason - steal your time and give you nothing instead. People who make them are the worst. But let's return to the bright side of cartoons.
Another interesting thing about cartoons is that we (adults) watch them in our free time. It is the time when we can relax from work and fly away from reality by watching cartoons. Well, someone plays computer games, someone watches films or tv shows, etc. If there is something that can help you to relax and to stay calm you definitely should do (at least while your hobbies are legal and harmless to others).
All I want to say is that you should do something because you like it, and don't stop doing it even if someone finds it stupid or for kids. This is your life, your choices. Anyway, life is too short not to do something that you like.