While I like Ash and most of the companions in SM, I admit the spotlight is incredibly uneven in the series.
I think a problem is that they've finally gotten a grasp on Ash in terms of colourful dynamics and agency, but are now over engrossed in that, only making token attempts to do the same with the others now (exacerbated by having FIVE of them this series). It's not consistent, there are SOME great episodes with the other characters, but there's just too many where Ash does all the battles/slapstick/character development moments and everyone else is just kind of standing in the background not really involved, sometimes even in an episode they're supposed to have a main role.
Ash is also constantly JUST on the very borderline of being the series' designated monkey, they'll have a chunk of episodes that tend to pick on him and no one else and just make him by far the most inherently flawed and luckless character, only then they'll craftily place in a few everyone else gets their fair turn of slapstick and self provoked misery. I always have a wary eye waiting for the balance to finally dip (the Poni Island arc is currently in another 'Only Ash gets hurt/humiliated/looks fallible in any way' faze).
It's frustrating at times because there are always glimmers of great traits and foibles for the other characters that would make them great for central roles if they played on them enough, but the writers often seem to have a 'Why use such-and-such-character when Ash can do it fine?' outlook and have to force themselves to try and focus on the others. I liked the spa episode for example since it played with a more high strung side of Mallow from suffering Ash's hijinks for once, this flaw for her is seldom seen elsewhere of course because she's almost never the butt monkey compared to Ash. Also the very few episodes Ash has a minimal role, like Lillie's first Poni Island episode (while the recent one had Ash more or less steal it from her).
It'd be nice to have a series that could keep a damn balance for once, not keeping largely to either 'Only Ash does all the fun stuff' or 'Only everyone BUT Ash does all the fun stuff'.
