Let's talk about Serena's character. Does anybody feel that Serena doesn't suit being an idol? Idols need to be more lively, playful, and genki, but Serena is too reserved and meek. Furthermore, idol fans can't stand their idol dating or showing interest in another man, meaning Serena would have to remain single to maintain her career and can not make any move on Ash. Honestly, Dawn is more suitable as an idol due to her genki personality and disinterest in romance, while Serena fits better as a Pokémon stylist.
JN series messed up , they should have turn Serena into a Pokemon stylist or actress.