I also didn't mind Ash losing the league constantly, but for a completely different reason. I never really believed he deserved to win.
Eh, let's take a quick look through each league/major competition Ash has gone through before saying that:
Kanto: Suede episode reviews I linked to above, notably for Episode 80, actually addresses this. Ash lost because he got lucky in a few of his early League battles so got cocky, ending with him using a Pokemon he can't control that costed him the match (also not training his Pokemon and using Pokemon he never battled with once). Ritchie was essentially made to be the antithesis to Ash, he was a strategic thinker and came into the battle with a plan and Pokemon he trained well. And with Ritchie using similar Pokemon as Ash used it left Ash simply outmatched.
Orange Island: For a while was technically the exception to the rule Ash loses all Leagues he entered... though Orange Islands don't exist in the games and most people only care/count the Leagues which came from the games. Also Ash didn't have to battle in a tournament, once he got all the Badges he automatically could challenge the OI Champion.
Still, him winning against Drake was nothing to shrug off. Drake had a pretty strong line-up, or at least the writers we able to make us believe that. Starting off he used a Ditto which gimmick was copying whatever Pokemon the opponent sent out. The announcer said many challengers never get past Ditto as they don't know how to handle the mirror matches. This doesn't just show that Drake's Pokemon are all tough and have their own unique challenge, but subtly hint how good of a trainer Drake is. He doesn't know what Pokemon a trainer is bringing in yet in mirror matches he's able to command Ditto to defeat a trainer's entire team. No wonder when the little guy came in it was flexing... and when Ash defeated it without losing any of his Pokemon showed Ash was a step above most other trainers.
Drake's next four Pokemon was just a show of power and that Drake has trained a diverse team. Onix size provided an intimidation factor and used Dig to make the opponent worry about the floor it stood on (it also could grab a hold of you but in this case was its downfall as it did this against Ash's Squirtle which can spray water from all holes in its shell...), Gengar was a trickster using Confuse Ray and Hypnosis, Venusaur was a bulky wall that even a toss from Tauros didn't stop it from using Solar Beam in midair, and Electabuzz was both a brawler and powerhouse.
And then finally was his Dragonite. They purposely made his Dragonite overpowered by letting it use as many moves it needed to do to seem invincible. Despite how tough all the other battles were Ash actually went up against Dragonite with 4 Pokemon. However it took no time for Dragonite to knock out 3 of them (which includes Charizard that Dragonite defeated by grabbing it during Seismic Toss and slamming it into the ground instead). It even took a second to send Team Rocket blasting off before facing Pikachu in a dragout battle where Pikachu barely won by landing onto Dragonite's head and unleashing the strongest Thunder it could muster.
So while Ash didn't go through a tournament to challenge Drake, him defeating Drake and entered into the Orange Island's Hall of Fame was well deserved due to how overpowered they made Dragonite not to mention how tough of challenge Drake's team was.
Johto: Ash's lost in Johto was a bit on the iffy side as it was essentially to advertise Gen III. Still, you could say that, while Ash was more experienced and had a better trained team (plus his reserves and a Charizard that listens to him), Ash lost was due to him being unable to adapt to a mystery opponent. That's not to say Harrison's other Pokemon didn't provide a challenge, both him and Ash sharing knock outs, but it was definitely Blaziken's show as it took down Ash's Charizard. Of course the battle did leave Harrison in a bad place as Blaziken was too tired to fight in the next match and Harrison was knocked out next, so even though Ash lost he still left a lasting impact (oh, and let's not forget that just before Harrison that Ash defeated Gary which was probably the more important match to be honest).
Hoenn: Tyson was just a really tough trainer, infact he went on to win the Ever Grande Conference so you could say Ash was facing a pseudo-Champion. Another factor was that Ash didn't use any of his reserves, and while his Hoenn team was a pretty good line-up, it had a hard time holding a candle to Tyson's which included a Metagross. You could also say Tyson had a special Pokemon with his Meowth-In-Boots, both it and Pikachu having such a tough battle they did the anime trope where both are too exhausted to battle so the first to fall loses... and in this case it was Pikachu. Tyson was pretty much an example of "there's always someone better than you".
Battle Frontier: Let us not forgot the other major victory Ash had and it was something from the games: beating the Gen III Battle Frontier! The Battle Frontier arc actually showed how much good of a trainer Ash can be when the battles aren't exactly your standard fare. Ash's strongest aspect, at least at this point in the series, is being able to adapt to quickly changing battle situations. And this was what the Battle Frontier was all about, having these unique battle scenarios that most trainers may struggle keeping up with but Ash excels at. It's no wonder he impressed Scott so much he was invited to become a Frontier Brain. Of course he denied as he wanted to continue travelling, though curious if that position is still open for him (too bad Sinnoh skipped it's Battle Frontier as we could maybe have had a follow-up...).
Sinnoh: Ash did everything right this league. His team was pretty top-notch, he was using his reserves to full effect, seems like the only way for there to be someone better than Ash was if said trainer was using Legendaries!... And that's exactly what the writers did. Yes, we've now come to a turning point where Ash's loses aren't as much of his own experience and decisions and more just the writers not wanting him to win so creates a trainer seemingly just for that purpose. I could believe Ritchie, Harrison, and Tyson just being ordinary trainers that Ash just so happened to have to battle. Tobias on the other hand only exists so Ash would lose. Of course Ash was going to lose a guy who uses Legendaries. Heck, I'm sure he'll probably blast through the Elite Four with minor difficulties and may have a more challenging battle against Cynthia. At least Ash did knockout Tobias's Darkrai and Latios to show how far Ash has gone that he's even able to defeat Legendaries somewhat reliably (note the opponent Tobias faced in the finals didn't even knock out Darkrai).
Unova: AHH! F*** THIS LEAGUE. At the very least they didn't throw out random Legendaries for Ash to lose against, but then again the way Ash lost made him look pathetic. He lost to a trainer who only brought 5 Pokemon to a full battle because he's too stupid to realize a full party is 6 Pokemon (said trainer also through the Unova League was taking place IN JOHTO). Yes, we're talking about Cameron, who also thought you only needed 7 Badges to enter a League so Ash & co. had to help him several times to even enter the League. And what's Ash's reward? Well Ash honestly beat Cameron's other 4 Pokemon fairly easily, including his Hydreigon. Unfortunately Cameron also had a Riolu which in the middle of their battle pressed the "I win" button and evolved into Lucario to sweep Ash's team. Ash was also weaker as he didn't have access to his reserves and a lot of his Unova team weren't fully evolved. Though the most frustrating part about this is that they already had a trainer which I think everyone would have felt better for Ash to lose to: Virgil who used an Eeveelution team and who Cameron lost to next round. GAH! Did you really need to shove how awesome Lucario was down our throat that you couldn't have it lose so Ash could then go on and be the one to lose to Virgil instead?
*Heavy sigh*
Kalos: Now compared to Tobias and Cameron, Alain wasn't as bad as we did have a side series featuring him as the protagonist. And he did also have an interesting story where he eventually became a member of Team Flare and was Lysandre's top operative. Honestly what I think frustrated people the most about Alain beating Ash was that Alain's signature Pokemon was another super popular Pokemon, Charizard (which could Mega Evolve into Mega Charizard X which was the most popular Mega Charizard), and that Ash's Greninja was given a super special form change making it feel like Ash had finally gotten to that next level and maybe beyond. But nope, despite Super Greninja the one who still won was the guy with the popular Mega Pokemon. However Ash losing also played with the larger story as they needed to have Alain being the more powerful to put Ash in a rough situation (captured by Lysandre as he's interested in Ash's ability to transform Greninja into its unique form) and he's out of the way while Lysandre uses Zygarde to attack Lumiose City.
Alola: ... While I'm glad Ash finally won a major league, at the same time Alola League was kind of disappointing in the way they wrote the battles. Just sticking with the battles Ash was in, his defeat of Hau was just total BS. He should have lost, but instead the writers decided to thrown in a ton of gags concerning Rowlet which narrowly allowed it to have enough time to get serious and beat Decidueye who should have won two times over by the time Rowlet got serious. Oh, let's also not forget that NONE of the battles were full battles (because Ash didn't have a full team...), the only full battle was after Ash became Champion and Kukui challenged him to an exhibition match. And even that gets interrupted by Tapu Koko deciding it wants to do a Z-Move clash with Ash & Pikachu.
... So, with that all said, let me gather my thoughts:
Ash shouldn't win Kanto, Johto & Hoenn as they were the "learning" experience leagues. Each taught him something he brought to the next league to help him become better.
I think Ash should have won Sinnoh. He was at his best with both his regional team and his reserved team. Like you could still have him lose against the Elite Four, you still had that trump card. Infact Sinnoh was the first region which had all four of its Elite Four appeared in the anime (and the only one to have them all meet Ash & co.)!
Unova was an embarrassment, to me proof that the writers no longer had an interest writing a Pokemon anime unless they could turn it into another genre because their creatively bankrupt.
Kalos interest was the overarching story which was alright now looking back on it but still frustrating to the long time fans who thought Ash actually had a chance.
And finally Alola wasn't deserved. Hau should have beaten Ash and the Champion either be Hau or Gladion. Though I guess in the way Alola was the only League Ash could be Champion in as it was its first league so had no idea what it as doing.
