IX does a fair job compared to some other entries in the series. I do agree that some characters sort of just drop out of the plot (Freya, Vivi, Eiko) while others felt rather pointless and more like you were just filling up your party quota (Quina and Amarant) Steiner loses his relevance after the beginning of the third disc but it's because he resolves his issues rather early. I would say its not any worse than other entries. Even VII and X had some issues of you wondering why half the party was with you.