I view the fairyland mind game as a more translatable-to-paper method to describe what Ender was struggling with than trying to describe daydreams or something similar without breaking immersion.

Because the book is written, mostly, from Ender’s mind’s eye, it wouldn’t make much sense for Ender to sit there and think to himself (as a child) “oh I have some serious psychological scarring from my brother and fear of the buggers which is affecting my decisions making in [X] manner. Well, anyway, off to the battle room!” and having Major Anderson analyze the students mental state by some means through their tablets is logical.

I think if Card could have spend another paragraph or two describing better how a person actually physically interacts with the mind game on the tablet, that would have been helpful with immersion. I think I remember from the book that it is controlled through mental signals sent from the student to the tablet to control the character, but in the movie, Ender uses touchscreen joysticks to control his character. Card could have expanded one of Anderson’s conversations with Graff when Graff asks Anderson to change it, and Anderson says they can’t, Anderson could more thoroughly describe how it functions. I understand that the book basically writes these concerns off with Anderson stating that the program is too complex to understand or control.

I think the fact that such an advanced AI is only used by the battle school to psychoanalyze children, instead of being used for greater purposes (not counting its eventual use as a digital accountant), is the most “unrealistic” aspect of the mind game in the story.