Reading through Iseul's route (Love & Legends), I get the impression his writer was uncomfortable writing multiple characters at once.
Once you notice, you find characters mainly speak in monologues: the other characters only existing to listen, if they're not forgotten about mid-way. When multiple characters are in a scene, they will say one line each (if that) before immediately getting an excuse to leave.
Perhaps it would have worked for a loner archetype, but Iseul is the most sociable character in the series and this leaves him feeling detached from his best friends and his family. Even at his wedding (the peak of all their loved ones celebrating him and MC), characters say a line to him, he continues without responding, and he leaves his own wedding early to get away from them. Despite all they've been through, all the history and development, you end up feeling these characters don't even like each other.
Juggling multiple characters is a skill but... I wish it hadn't come at the expense of one of my favourite characters.
