I made a similar comment like this a couple months ago...it seems like it would be hard to draw the line on what to include and what not to include.
I'm considering getting a dumb phone for on-call and talking to my friends/family...but if I wanted all of that other functionality I could just delete the apps that are addicting off of my phone.
Then you can use maps stored on the device and get a modern camera and lots of storage and so on but you aren't constantly checking apps for notifications and whatever.
This is what I do. I use HERE WeGO for offline maps, check messages when there's wifi. Saves a lot of money too! Never experienced problems so far. I think it's easier when you never had a data plan, going 'back' might be tough as you've changed your habits to rely on a data plan.