Every kid-character was a thoughtless menace to everyone else around them without a shred of empathy. That’s great if you’re an adult who hates kids but as a kid, I didn’t want to identify with the characters at all.
I know Nancy Drew/the Hardy Boys were perhaps unrealistically intelligent for their age but I read them because I wanted to be like them. Why would I read about people who personify all the things I hate about myself?