Focusing on the phone seems like missing the mark. The addictive thing is not the phone, but the internet. Even with a dumbphone you can easily waste as much time on your laptop's web-browser (and people did: FB and Youtube were already big before the iPhone was a thing). Conversely, if you turn off data, there are not many possibilities to spend huge amounts of time on your phone. (And yes, there are still plenty of…
The good news is that you don't need to set a very high bar for a better use of this free time. Read a book. Go on a small walk around the block. Take care of your garden, if you have one. Do simple chores. Do nothing at all. Almost anything is better than smartphone usage.