The fact that this was Ash's last season, but most of the time he was either taking a backseat so the people in charge could focus on Goh and experiment with the new protag angle. On top of that, a lot of episodes slots on really dumb, unimportant slapstick episodes that didn't matter at all, like who cares about an episode blue pokemon or why should we give a crap about about that lab assistance guy's magnimite? But Ash's PWC gets put into offscreen land?
Goh catching a bunch of really strong pokemon so easily. That a beginning trainer that barely trains like him has any business catching fully evolved pokemon and Legendaries is sickening, and makes him come off as a complete writers pet where 90% of the world around him has to bend its rules to cater to and reward him, despite not earning it.
Ash having multiples of the same type, If they're gonna restrict Ash to just using just the five he catches, give him more variety in types, and on top of that not just speedy attackers either, he should be skilled enough to be able to train more tankier pokemon. I really feel like they didn't put any actual thought into his team and kinda slapped it together to be done with it.
Ash not catching anything new after Dracovish (That was 86 episodes ago btw) and even though the five he caught didn't get the development they needed, thats just a whole different problem that I'll bring up next, but it still got boring and stagnant really fast seeing Ash the same team for 86 episodes, JN wasn't even half over by the time they filled out his team. Or at the very least him use and Evolve some of his reserves along along with the 5 catches he was locked into. I Also feel like the repeating types were an excuse to not give Ash more varied opponents, Like we saw him fight three dragon type experts, two electric type experts, and have three fights with Bea. And for god sakes there were three Dragonite users in the M8.
Now onto Ash's team. the Pokemon that are supposed to be the important ones in the show. Outside of the few short onscreen battles we see them in, the Pokemon on Ash's team barely got an any onscreen development.You know how a lot of people were saying Lucario would be the screen hog pokemon, but we only really see him used in battles. Instead most of the time, Ash only brought Pikachu, and this ties back into my complaint about being too much dumb and unimportant episodes, remember that really unnecessary episode where Pikachu got upset because Ash was trying to train Riolu, well apparently they tripled down sentiment by A. making it so that Ash pretty much forgot his other Pokemon in the non-PWC episode and B.) dedicating episode time to Pokemon that don't matter, like did we really need an episode about one of Goh 5 Floettes? Am I supposed to care about some random ass Psyduck he caught? You could also argue most Chloes Eevee episodes are similarly guilty of waisting (I thought the water race episode was pretty fun since Dracovish got to join in)
That and he didn't get more Galar or any Hisui rep either, especially since there a ton of pokemon released in Gen 8 that would have been amazing under his ownership, including the other two Galar starters, both of which would have been better under Ash's care. Sobble because instead of moping around getting two unearned evolutions, Ash would have been able to instill courage in it, working hard to earn its way to Intellion, and Grookey could have channeled all that rambunctious energy into battling, instead of being a brat.
Speaking of Galar, holy crap did it get shafted! More than half of JN was a took place in Kanto, which makes suspect gen one pandering. There's also the fact that a number of original game characters didn't make an appearance in the show.