It was a slow burn, but once it caught fire, it exploded. Intentional or otherwise, the league picked up momentum as it went on, culminating in some truly memorable moments, which I think is exactly what you want for something which spanned so many episodes.
The early slowness can be attributed to open nature of the tournament and the decision to show every match. As anyone could compete, there was a build-up of characters who, while recognisable, were not very significant to the story. Each of these characters then got a match. Whereas past season have skipped to the conclusion of early battles, SM decided to give them full matches, albeit mercifully short ones. The benefit of this was that it gave the weaker battlers such as Lillie, Mallow and Sophocles an opportunity to do something and have a moment when they otherwise would not have. The downside is that if you're not enamoured or invested in these characters, it's going to feel like a slog. The 1v1 format seemed to be a compromise between giving these characters a chance while also keeping things as breezy as possible.
What I appreciated the most about the league was that everyone got a chance to shine. This was especially notable with Ash's team. Meltan gets a win, evolves and contributes in the final and exhibition match; Rowlet defeats Decidueye; Naganadel got a strong showing in the last two matches; Lycanroc overcame Gladion's Lycanroc to win Ash the trophy; Torracat defeats its rival Incineroar and evolves; and Pikachu defeats Tapu Koko, who had beaten it twice in the serious before then. Nobody felt underused or sidelined. At the same time, nobody felt more special than the others, either. The league should be a crowning moment for Ash's Pokemon, and this one delivered on this front.
Ultimately, the whole league was elevated by Ash's victories. He defeats Guzma, the supposedly unbeatable trainer. Then he defeats Gladion, who had won every battle between them beforehand. Then he even beats Kukui and Tapu Koko, the so-called strongest combination of all of Alola. Kukui even remarks how Ash grew stronger as the tournament went on. We're so used to tournaments ending on a downer that all of this was an amazing surprise.
There were some smaller things the league did well, too. Ash's friends were more interesting to watch in the crowd than in previous seasons, because they had a level of investment and expression than went beyond them. Ash's reaction to winning those big matches were nice, too. The shock he actually won the final vs Gladion, and then the exhausted contentedness after defeating Kukui were better choices to me than raw elation. Also, plus points for having Delia there to see her boy finally win the big one.
As a showcase of battling, there have been stronger leagues. The battles throughout were simplistic, with little strategy deployed beyond using the strongest attacks available. Even Ash vs Kukui lacked that strategic element to it, despite being an extremely fun spectacle otherwise. I thought this was the league's biggest downside.
