I think smartphone use has split into two paths: utility and "discovery." Utilities are the tools we use every day, the tools we want to be stable, fast, and (relatively) unchanging. E.g. sms, maps, browser, phone, camera, email. "Discovery" is all the new, unstable, changing stuff. I think there's an enormous market for a utility smartphone...and it doesn't even have to be a smartphone. Something between an old Noki…
Wikpedia(1) says in the US its actually: Facebook, Facebook Messenger, YoutTube, Google Maps, Google Search, Google Play, Gmail, Instagram, Apple Music and Amazon
For other countries you just have to swap out Messenger for Whatsapp and such...but otherwise its basically the same.
Mind you this includes preinstalled apps!
So I'd say if anything, someone should build a Facebook phone, without all the other crap like phone, email and sms apps :)
(1) https://en.wikipedia.org/wiki/List_of_most_popular_smartphon...