The big thing though for this context is Ash has ties to the Gamefreak games, while Goh is more based on Pokemon GO. And overall, GO vastly out earns the mainline games, so having a character connected to the better selling games makes more sense. Also how one of the big creators inside of GameFreak has gone on record saying he figures kids don't stick with the games after they beat the league, they go play on their phones. I have no clue how much Masters EX makes compared to the rest, but GO is a silly big earner, making most of the games profits. So it makes sense that they would move away from Ash, and on to Goh, who represents a game that the makers think more people play, and earns more, and has no end state for people to get bored with. Also he more actively catches mons, while Ash get 5 to 7 then stops. Seems like he would make a better lead for a series about catching mons, and disconnecting the story from gyms might make more options for major plot lines. And they would even be able to have a companion who is interested in the gyms, and not be Ash, or the lead. Which opens the role up to someone else, who makes more sense to struggle with gyms, and can have a story line that doesn't need to continue after the region is over. Heck, they could finally even have the girl companion be the battler, who's seeking the badges. It always felt a little strange how they had to shove the girl off to the fashion contests, which is likely why they grabbed Iris for gen 5, rather then bring in Hilda from the games. Having an aspiring gym leader meant they didn't have to have her getting badges, and they didn't have to turn the battle maiden, which is what Hilda as a name means, into a frilly contest/dance girl. Which is one of the flaws of that arc of the Adventures Manga. Given how the games played out the story, I feel Hilda works best as the canon rival of N, though I'm not sure who works best as canon character of the sequel.

They might just be doing a short run of Goh episodes before we get back to Ash going to Paldea. But I feel it might be cool to move on to Goh and start getting new characters who can do things Ash kept getting shoved into doing when it made little sense. Like new trainer struggling at gyms, in particular.