It's because even children can be scarily good at specific things. I have a cousin (she's a child) and has a YouTube channel, knows her way around content creation to a basic extent but absolutely can't print a document or use MS Word. She was good at using phones when she was a toddler. So she got really good at the things she cared about and didn't bother with the rest. The older generation didn't have stuff like this to begin with, so of course they would take longer to learn stuff than a person who lives with it and around it from the time they were born.