Neat! It's great to see this segment of phones increasing. Cal Newport in his book Digital Minimalism talks about why he prefers the term "digital declutter" to "digital detox." A detox makes it sound like a break and you'll eventually go back. Like the case of getting a dumb phone, a digital declutter is sorting out your relationship with technology and keeping only what's useful. He uses the analogy of decluttering a house. You don't just randomly throw stuff away. You take inventory of what's useful and what isn't.
I don't care for the term digital detox as it's used here either for the reasons you state. My iPhone is on its last legs and I'm pretty sure I'm going to replace it with a dumb phone. I've even contemplated getting a landline again.