Honestly, It's Probably the Phones 3 years ago
There will be many answers about a technical solution for this (apps that limit apps, dumb phones, different launchers etc.). None will work.
Train yourself to not phone. Same as you can not consume advertising (cant adblock billboards).
All the technical solutions trim too much away about what makes a smartphone great, or add too much friction, either to configure or to disable again, which you will do anyways. Also these technical solutions are just products again. They exist not to actually work, but to make money. Sometimes both are true, but rarely.
This is a two tier society. Those who can train themselves to do this, who will be able to read books, learn, be present without Soma and ...
the zombies.