If that were the case there were only two options: Either they should've made the Alola League more memorable and of higher quality, or they should've just made Ash win the kalos league. There was no reason to have such high quality Kiawe vs Gladion battles and have the rest of the matches be nearly B&W level of bad. The Grand Finals were low budget and mediocre as fuck with only the Zoroark Z-Move stuff standing out. They should've gotten more invested in such a big moment in order for the episode to actually live up to the name of the event, because before the victory, the hype was near nonexistant.
It was either that or just letting him win the Kalos League. By then word of mouth had already spread and hype was developing greatly, especially given the fact that it was the first time Ash had reached Grand Finals and lots of people were aware of the now useless foreshadowing of his victory. Hell, i hadn't watched the anime since Hoenn era, but some normie friends convinced me to watch it around the time Ash was about to battle Shota and that managed to convince me to keep an eye out for the league. For a moment it got pretty big and even i was getting convinced he would win. It was maybe the best possible time to make Ash win, but they decided not to for some reason.
The problem is that they expended his first big league win in such a halfassed manner. Now if Ash remains the protag and he gets an actual high stakes league of tremendously high quality, the impact of the win will be deadened because he's already won before. I would be okay with Ash winning this league if they had put enough effort to properly represent such a historic moment.