I haven’t watched the anime since the start of BW, but I kept up with what plot points. Maybe I’m missing something but:
Serena was fucking pointless. She was every shounen female trope in a nice package with a bow. Crush on the protagonist? Check. Soft spoken and meek? Check. “Character development” defined by chopping her hair off? Check. Seemed like she dicked around the first year of the series because she (the writers) didn’t know what to do, only to pick up a goal that was an uninteresting and watered down version of May and Dawn’s goals. Her only memorable contribution was the “will they or won’t they” teases with Ash, reminiscent of friends and the office.
I quit watching the anime because iris was so obnoxious, but I still hold the opinion that Serena is worse than her