One reason could be the unrealistic portrayal of love. Love novels often present a perfect, fairy - tale - like love that rarely exists in real life. It gives people false expectations.
Toge Inumaki is important too. His special cursed speech ability makes him stand out. Also, the principal of the school, Masamichi Yaga, is likely to be important as he is in a position of authority and has an influence on Gojo and the other students. There could be other characters like the members of different clans that also play roles in the complex web of the story.
You can write reviews highlighting the flaws. Point out the overly simplistic characters or the predictable plotlines. For instance, if a love novel always has the same type of hero or heroine with no real depth, mention it in your review.