(this is me speculating)
1) Side characters. S1 & S2 introduced us to characters we ended up caring about (other than Ryo). This really didn't happen in S3 and given the ending sequence shoe-horned in broom girl and the dude who gave you the forklift job, I'd argue it's clear that there is content missing to flesh out these characters. Other notable exceptions include Mr./Master Feng, who ought to have explored your father's history with you (Ryo seems strangely lacking in curiosity WRT his dad here given his current vendetta).
2) Niao Sun's character arc. Similar to the side characters who showed up out of no where to help you in the castle, Niao Sun showed up out of nowhere to become a baddie at the very last minute. There was clearly some hints she'd try and put a wedge between Ryo and Shenhua, but this never materialized.