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 wonder if there is a niche market for something like an old Dell Axim x50v or a Palm Pilot that could do those smartphone functions on a wifi connection, that way you have the best of both worlds, carry a dumbphone. However, you could still walk into a local Library or even some McDonald's and connect if need be on the other device.
Of course, then you have to inconveniently carry two devices and the temptation would probably still be there.
Only wifi you'll get on one of those has to be an older wifi standard without modern encryption. I can't get my PDAs to connect via my router, but if I make a wifi Hotspot on my phone with no encryption or password, I can get mine to connect. Even then, HTTPS websites largely won't work since these devices are pre https-as-standard.
Beyond that however, I find a lotta use in mine for helping manage my ADHD since it does a lotta productivity stuff my phone can do, but with the only distraction being my mp3s and Space Trader.
That's why I said I wonder if their was a niche market for something like those devices, meaning I wondered if some company could make a newer modern version, like Apple used to make the iPod Touch for a while, which were almost the same as the iPhone just without the cellular connection.
I mean, they're quite literally designed to be as addicting as possible. I can't blame people for getting addicted to social media when billions of dollars have been invested in research on how to get them hooked.