That is a factor, but not a big one anymore. Not as big as the communication chips (bluetooth, wifi, 4g/5g). Also rendering apps and websites is excessively expensive, specially if you want to have HiDPI and 60Hz or more.
I'm typing this comment on a Zenfone 9, which is a pretty reasonably sized phone with a decent battery and camera. Charging to 80% usually lasts me over a day of usage. The camera is good enough as well. Phones don't have to be so massive to have those features