I feel this is a reductive argument. Parents should help their kids avoid harm while also encouraging growth. Phones and the Internet can absolutely encourage growth. The parent's job is to ensure that the phone isn't harming them. If the kid isn't on the phone too much, isn't picking up bad shit from the phone, and isn't harming anyone else, I don't think it makes sense to deny them.

If the kid is being harmed by being on the phone, then the parent should try to figure out what the problem truly is so they can find good solutions. I was on the computer too much as a kid and missed out on important shit. Rather than ripping out desktop out of the desk in a rage (which is what happened), my dad should have thought about why I felt the need to escape from my life so much (e.g. being afraid of a father who would do shit like rip out a computer and threaten to throw it off of a second floor balcony, self hatred, intense bullying at school, or alllll the crazy shit my mom did). He didn't try to help me fix the things that were harming me, so all I had was my computer and the few people who didn't seem to hate me.

I spent so many hours browsing Wikipedia, learning about scientific concepts. I talked to people who had lives like mine and were able to commiserate. I found a place and community that I was lacking in my everyday life. I learned skills that eventually translates to a successful career in software development. I don't think that it's good when kids feel like they need to escape to the Internet, but I think that having access to all the great stuff out there is worth it. For the kids who have awful lives because of shitty fucked up parents, the internet (or any escapist coping mechanism) can literally save them, albeit at a substantial cost.

The internet can be harmful, but we only seek out harmful things when the alternative is going without things we need. I think this is also true of children, so the question I feel parents should ask is "what does my phone-addicted kid need?"