Let me just say that this episode was needed for the sole purpose of showing off what else Pokémon Connoisseur's can do. Therefore it's not filler.
To be more precise- It's not a filler in between two canon events; Finding out Opelucid Gym is closed in the start, going to Virbank City in the end.
I mean we were going to find more about them eventually. That's for anyone who thought this episode wasn't needed as Cilan got no development.
Fact 1: Cameron/Kotetsu is not disliked by everybody, stop saying he is, there are people in the fandom who do like him. I am one of those people.
Fact 2: The majority of people who like unpopular characters are always the most nicest and sensible and, therefore, the best people of the fandom.