Kinda true, but reason why there wasn't done much with him in second half was probably because they intended to replace him once 6th gen comes out not seeing need to dive more into character. If they planned to keep Cilan for longer they would put more effort into him to justify staying. Still you could feel his presence in most episodes through personality and interests being more active compared to Brock. And he battled incomparably more wishing that rivalry with Burgundy was more exploited, but alas.
Regarding Misty i don't know what to think lol. We had HGSS remakes and they dropped opportunity. Than BW2 games came up and World Cup being perfect since it could both help move her story and current plot forward.
But once again nothing. Than they go all in with references to Kanto and return of iconic first generation characters like Charizard, Clair returns, Brock is announced to come back in Cilan special etc. They had plenty of opportunities to bring her for at least one episode, be it in DA arc helping to promote games, at Pallet to have aside Brock meeting Cilan, have Misty meet Iris too but they avoided on all of them.
If they could have returned Jasmine, Jessibelle, Butch and Cassidy,Locker etc there was no reason why they couldn't fit her in somewhere in last 7/8 years.
She is popular, many would like her back and its kinda obvious how her story wasn't fleshed out as much as it could have been having room left to do more.
I say give us new characters, but dont abandon previous creations and started work about them bringing them back for sequels/for season or half a season(like N or Alexa were), thats not long and can give them proper tying and some more spotlight). Especially if they are in new games. Wouldn't that be better and more endearing than current state of things? At least to me it would bringing unexpected suprrises and shaking things up from time to time.
But meh, i came to acceptance how its not smart to expect much in this show.