Had a OnePlus One, went back to a feature phone (an Alcatel flip phone, not the most sophisticated thing but I already had it as bacjup phone).
I miss nothing. No immediate pestering, no constant urge to look things up, improved navigational skills (if you can't use Google Maps for everything, you'll learn how to navigate around), no loss of concentration.
If people want to reach me, they can call and text me. There is no other messaging platform that is necessary so I don't care about anything else.