#its intro brushes past the ua traitor plotline and is intrinsically tied to Toga's whole character arc

[delawaredetroit]

Controversial take, but the crush plotline being introduced at this time in this way makes sense and helps move the plot forward. (The problems with this plotline are more that it overstays its welcome and takes up too much of Ochako's screen time)

It's logical that Aoyama would pick up on Ochako's crush because he was keeping an eye on Izuku. He doesn't know how Izuku is involved in the All for One/One for All conflict, but because one wrong move could get himself and his family killed, he has to pay attention to Izuku.

And it makes sense Aoyama would bring up the crush here; he is trying to sabotage Ochako's exam and he needs a distraction. Pointing out her high school crush out of the blue is an effective way to accomplish that.

Beyond that, this crush plotline needed to be in play before Toga - Ochako's narrative foil - was introduced.

Anyway, regardless of your thoughts of Izuocha, for a Shounen Jump romantic subplot, it's pretty intertwined with the main storyline.