I legit don't like some people right now.
How many of these people that would say "Ash didn't deserve to win this league" would hold it against Ash "See Ash is so weak he can't even win a league that's meant for baby trainers?" if he didn't beat Gladion. There's really no pleasing anyone is there.
The only reason I'm not super happy, is the idea of Ash being retired after this crappy generation, at least in context to Ash's development, growth, character. Ash shouldn't be given a relative freebie win just for them to justify "Introducing the brand new anime protagonist, FAREWELL Ash"
And don't get me wrong I'm not saying that this win didn't do wonders for Ash or his Pokemon but I have to point out what this series was. A jumbled mess of slice of life episodes, that clearly never knew what it wanted to do. The Grand Trials were a mess, the stories between them were a mess, it almost felt like most of the writing for this series was: "*YAWN* Another episode of Pokemon......OH SHOOT we're supposed to do something important, weren't we?"
For Ash to be concluded after this series, I feel is a complete disservice to his character, but I think I'll argue that while Ash was the "most" focused on of the characters, and was the protagonist of this generation, he does ultimately feel just like a character where something amazing happened to him. Not anything stands out, it's just Ash who happened to win the Alola league.
But I guess where the Alola region really shined more than any generation was focusing on so many other characters, it wasn't equal nor fair and some like Mallow were horribly screwed over, but where Alola shined was its personality. I do think Alola had the most personality of all the series, there definitely was always a bright mood when it came to the episodes and the characters. The character interactions were fantastic as the series allowed it to be.
But is this really how you want to end Ash as a character, giving him a win to a league that he HAD to win, without being called weak as hell. I'd argue that if Ash didn't win, his Pokemon would be viewed as weaker than they need to be, I mean compare Ash's other losses. Was Gladion really truly the person Ash needed to lose to when compared to everyone else with the exception of (Ritchie).
For a character we've had for 20+ years, the final HURRAH for the character just wasn't this series. Now I've said this multiple times before, but the proper way to retire Ash, is a region/series devoted MOSTLY to Ash, heavily to Ash (yes at the chagrin of the people who hate the character), have a lot of focus on his Pokemon. Show Ash being very competent in his battles, quickly go through the regional's gym challenge quest, and enter the league and win, all in a short amount of time (like at least leave a year for the final arc of Ash). Then the final arc could be mostly about a giant tournament where Ash uses ALL of his Pokemon that he has access to, runs into all past generation characters, and like I said before, the final episode has Ash reflecting on what he's done throughout all the generations, gets up (if he was sitting), Pikachu climbs his shoulders and Ash says something along the lines "We've done a lot together Pikachu, we've come so far. With all the rivals, friends and enemies I've encountered and all the Pokemon I've met, there's still more to do and more people and Pokemon to meet. Our journey isn't over Pikachu, it's just beginning." (anything like that is fine, it doesn't need to be exact. And then Ash can walk off into the sunset, and we never see Ash again, that's how you'd retire Ash. Not a disorganized series with a weak league that Ash wins that just hastily concludes Ash as an afterthought.
As for the people who hate Ash: Not sure why you are complaining, this might mean you get your wish of never seeing Ash on the screen again. It's not confirmed but you can always hope.
So ultimately, Ash did win a league, but I'm going to be very bitter about how it gives them an excuse to write off the character because they've finally decided to try something new. At the very least of it though, even if Ash does continue, the small summary of the new generation makes it clear it WON'T focus solely on Ash as Ash's last hurrah, so I really don't know how I'm supposed to feel about this.