Zhydra
Master of Chaos!
Ash could win, they just could have it that because he's on his Pokemon journey the runner-up gets to keep the position. That way they can explain why the show can keep going on when Ash is champion, the difficulty of which being the REAL reason why Ash only wins filler leagues
You forgot that title defense is a thing in the Alola Games. Where you become the Champion that others try to beat because they want that title for themselves. So you crush them like bugs!
Ash wins the league... maybe, he relishes his title for a few episodes and then loses it towards the end of the series. Resetting things to the status quo while giving its own twist to it.