personally, I somewhat enjoy going through these events even if we already know this information. I think we're getting more insight into the characters, which seems to be more of the focus than the plot in this arc, and hopefully we'll get an explanation of how the Millenium Earl and Mana Walker were both present when Allen akumatized Mana. although it is dragging a little bit, I doubt it would have been enjoyable (or heart-rending, take your pick) to just plop into a flashback simply of when Allen was cursed.