It does feel a bit empty in some ways, totally agree. But having played City within the past year, I think that's down to Origins having a larger, more spread out map rather than less to do (bar 100000 less Riddler trophies thankfully). City gave the illusion of a busy world thanks to all the detailed art, neon, building signs and smaller scale but still just had gangs of thugs stood around. At least Origins had SWAT teams and anarchists to punch too.
Origins is a lot more linear and lacking in variety compared to City, but it didn't bother me weirdly