They’re okay. Definitely are not the best arc I’ve seen but they are not terrible. But still, there are a couple of them that I felt were really lackluster and could have been handled ten times better than they were in the series.
I would rate them like this: Akala, Necrozma, Ulu’ula, and Aether.
Akala: this is, by far the best arc I have seen in the SM anime so far. I was not a fan of the fact that Lana got a Z-Ring initially but I’m fully okay with that now. Ash’s battle with Totem Lurantis was okay, nothing really special if you ask me. The real thing that made this arc stand out to me is Ash’s battle with Olivia. That was, by far, the best battle I have seen in the SM anime. Such a great battle. Also the episode where Rockruff evolved into Dusk-form Lycanroc was great. Overall, this arc was great and was definitely the best one so far.
Necrozma: I’m not gonna lie, this arc was great but it also has a lot against it as well. I did like the conclusion to Poipole’s story and its farewell was the most heartbreaking farewell I have seen but the rest of it was extremely rushed. Plus, Team Rocket got so much buildup, only to do basically nothing. This arc could have been a lot better if it was a little longer.
Ula’ula: it was nice to see Ash go to the island without his classmates. I quite like Nanu & Acerola, Lycanroc’s battle with Tapu Bulu, and the battle Pikachu had with Mimikyu. That’s really about it. Team Rocket getting a Z-Ring was poorly handled, Rowlet learning Razor Leaf felt really underwhelming since it didn’t do anything. But the worst part was Ash’s battle with Nanu. The idea of having it be a 1 vs 3 battle but Ash falling for Nanu’s taunts really got on my nerves and the battle as a was really underwhelming.
Aether: this arc had the potential to be really good and it wasn’t. It was poorly executed, extremely rushed, and overall the worst arc I have seen in SM. I did like the concept of having Ash’s classmates do something by battling Lusamins’s Pokemon instead of following him around to do ultimately nothing. Lillie breaking Clefable out of Nihilego’s control came out of literally nowhere and felt out of place were all pretty bad but by far the worst part was how Ash got the Pikashium Z. All his Z-Ring was glow, the Electrium Z turned into the Pikashium Z, and then reverted back to Electrium Z. Like what? That made no sense and it was poorly handled. It would have been so better if Gladion would have been the one to use his Z-move to rescue Lusamine instead of Ash. Worst arc yet.