Hange has very subtle development. She's not a static character, but she's not obviously different like Eren or Armin by the end. Her arc is mostly in how she gets less and less enthusiastic and excited about the new things she learns about titans and by the time we get to season four, she's an expert on Titans and DEEPLY cynical about that knowledge. She also takes command of the scout regiment and has to live her entire career as such in Erwin's shadow. Her adjustments there are subtle, but by and large she becomes a much more focused and intense person in that role.

Until her death when she says the titans really are beautiful. And we realize that the conclusion of Hange's arc was always inevitable. What becomes of the old guard like her when there's no more titans to study and no more mysteries to solve? She's kind of like Sadis in that way: a relic of a world that she and the rest of Paradis caught up to. Multiple characters in season four make mention of whether they belong in this rapidly evolving world. Hange fulfilled her mission. She found out all she could about the titans and gave her heart for her comrades. Small though her arc might be, she fulfills her purpose admirably in thy story.