IMO a lot of the visual appeal of smartphone apps, mainly social media, would go away with small screen. I remember using my HTC desire to read the web and if it wasn't text, it was not great.

BTW the best form factor phone I had was the Nexus 4, at 4.7". I would very much like that back, but without that slippery glass back, repairable, held together with screws, with replaceable battery, shipped with LineageOS or /e/. Yep, I'll keep dreaming.