Theres this weird point in the game after summer break where you're integrating futaba into society. There are no palaces and therefore no goal. About two weeks of worldbuilding.

Then as soon as summer break ends you go to school for like 3 days and are immediately thrusted into the week-long Hawaii event. No palaces. No goal.

After that you have to deal with Morgana's episode for a few weeks which finally lead to Haru's true introduction.

It's essentially a full month and a half of doing absolutely nothing as the phantom thieves. If that time was dedicated to introducing Haru as a character via an additional palace (Possibly through Haru's fiancee), then her character wouldn't have suffered as much. She was ultimately overshadowed by Morgana's existential crisis.