First: I have really nothing against Chaeyeon, I adore her since the beginning of Produce101 and thinks that she is a absolutely stunning girl.
Second: I don't know much about Dia so maybe I'm wrong.
Third: I only see Chaeyeon, like her screentime was so so much? I really love her but seriously I could grasp only glimpses of the other members before Chaeyeon appears again? It was almost a Chaeyeon mv...
This is just my opinion so please respect that..