I honestly don't get this complaining that side characters should receive more attention than the main character. It makes no sense. If Ash's companions got most of the plot gravitating towards them then they would be the main protagonist -_-
It's not the whole getting the macguffins handed to them, since that's expected in any series (and I would be hypocritical since I like SM which is already doing the same thing with the Z ring/crystals). Ash can at least justify the possession of them most of the time since he is a genuinely competent trainer and is more than likely to use his powers to assist/save people than raise himself to the top. I will admit always giving the protagonists big unique boosts no one else can or make a substitute of is rather unfair though, but as mentioned many times AshGreninja was pretty much just an alternative for a Mega Evolution anyway, so most of his main opponents could match him.
I do tend to get annoyed when the entire plot CONSTANTLY gravitates towards the protagonists winning everything just because, and not just good guy/bad guy situations which have some justification either, even just standard matches and competitions things will often contrive in some ridiculous manner so they come out the winner. If you keep handing the protagonists victories that means they aren't earning them, and so they aren't proving WHY they should win. And the whole 'Oh but they try, they're good people and deserve it' doesn't cut it either. Not every opponent is a bad guy, some are as virtuous and put as much effort into things, and if anything deserve to win more because they don't get some ridiculous plot boost in their favour either.
Party Dancepades was so obvious in this it almost felt self deprecating. James was so jaded you felt sorry for him, he knew the moment Serena got Eevee to evolve just by luck of plot he was screwed, despite fighting better than her and there being no real stakes to require her to win. Hell, James didn't even want to fight and see Inkay get pummelled, and yet the narrative rooted for the twerps creaming him and Slurpuff and treated them getting the upper hand like Eevee and Pikachu were going to DIE. He couldn't avoid the humiliation since the plot always took their side, even when he was being more competent than them. THIS is bad plot bias for the protagonist.