The way the main character was just constantly focused on the friend and comparing and contrasting her life and her friend's life and the endless competition (but with the narrator of course being superior in her intellect) just was not interesting.
So I found the relationship fascinating, and to me the whole point (hammered home in the title, My Brilliant Friend) is that the narrator recognizes that *Lila* is obviously superior intellectually and in every way, except in certain choices that determine the trajectory of their lives. The books are her attempt to reckon with that.