I don't think it's the phone itself that was the problem here, I think its allowing your teenager unfettered access to social media. TikTok, Facebook, IG, are not particularly healthy IMO. There is something to look at here with the loss of interest in reading and being creative. iPhones are in fact very good outlets for creativity, its just that children need limits within them just like anything else.
Parents should be engaged with what kids are actually doing on their devices and be able to set boundaries for their digital lives. I'm all for being creative, and I think digital tools can be a real boon to it. Making games, videos, digital art, programming etc. are all awesome, character building experiences. Scrolling through feeds for 9 hours a day watching celebrities do hand-jives and gossip, not as much..