I feel like you missed the point of what happened. It's not that people are just upset because Ash lost and meta logic. It's a lot more of the in series side of it. XY felt like a change of pace because of more character driven episodes, better character interactions, episodes based around Ash literally contemplating his skills as a trainer, and a lot more. This series was the first time where the female protagonist had an explicit affection for Ash. In addition to this, the final fight itself did not have the satisfying feeling that the match directly prior to it did. It looked like a cop out/reverse plot armor for the antagonist rather than a legitimate loss. This doesn't help the fact that the guy he lost to had almost no character and no development on his side while the fight prior, against Shota, felt like there were bigger stakes because of how much more rooted their rivalry seemed.

Speaking of the stakes, this was the first time that Ash made it to the finals. Not the semi's, not top 8. Finals. This means stakes are higher from the meta logic side of it (because of the hype of how Ash made it to the top 2 for the first time) so of course people would be more upset than normal.

It's because of how that felt different from previous seasons and how this series felt more serious compared to the previous ones. Of course you'll have the idiots overreacting, but I think it has more to do with how the series presented itself as something different