You have to decide for yourself. If you are having fun, it's definitely not a waste of time though.
Your parents value other hobbies above videogames because of these things, most likely:
a) They haven't grown up with video games and they might somehow trust the media that makes them appear like incredibly unhealthy, addicting, nonsensical things.
b) Social contact is less than with other hobbies, for example if you do sport with others etc. Of course you have chats in osu for example but it's not the same as nobody will deny (if you don't believe me, just look at the community: there are so many people being active in the forums and in chat and causing drama and shitstorm over things, and in real life they are afraid to talk to foreign people).
Your parents value other hobbies above videogames because of these things, most likely:
a) They haven't grown up with video games and they might somehow trust the media that makes them appear like incredibly unhealthy, addicting, nonsensical things.
b) Social contact is less than with other hobbies, for example if you do sport with others etc. Of course you have chats in osu for example but it's not the same as nobody will deny (if you don't believe me, just look at the community: there are so many people being active in the forums and in chat and causing drama and shitstorm over things, and in real life they are afraid to talk to foreign people).