A friend has had a dumb phone for a few years but supplemented with an iPad for things like messaging apps, maps, banking, camera. He finds the iPad just inconvenient enough to avoid social media addiction and always-connected mentality while still convenient enough to deal with the problems you described
I tried this myself, but it’s hard for a few reasons:
Some “dumb” phones still have a web browser and such, so you’re not completely out of luck, but it’s painful.
Right my phone is just a pocket computer, I only use it as an actual phone when I have no other choice.
A friend has had a dumb phone for a few years but supplemented with an iPad for things like messaging apps, maps, banking, camera. He finds the iPad just inconvenient enough to avoid social media addiction and always-connected mentality while still convenient enough to deal with the problems you described