Sergio Pereira, CBR:
One of the things that Murakami pushed for was to have proper character development on the show. He didn’t want a procedural animated show where it was mindless heroes versus villains action with no continuous storyline or progression. As such, each season of the show focused on a Titan’s specific arc.
Unfortunately, because the show ended after five seasons (and one season was dedicated to Terra), Starfire never received her own season. That said, she did get an expanded role in the film. Maybe if there’s a sixth season, there will be a chance to remedy this. After all, Koriand’r is a princess and deserves only the best.