Screen size was the compromise for me
My ideal phone would be no larger than my old Nexus 5, but when I decided to replace it I couldn't find an upgrade that ticked all the boxes I wanted for screen resolution, updates, memory, processor, memory, LTE bands etc (price rules out the new pixels) . The only compromise I could make was to move to a bigger phone (Nexus 5x). Now I'm shopping for a 5x replacement and I find I have to move to a bigger and heavier phone again just to get a decent upgrade.
Maybe big phones are selling well because there just aren't any options available for people like me?