Oh, and it wasn't out of character for Dawn to call Ash a kid?
Beating a bunch of kids isn't going to let Ash battle with the adults, winning the Orange League and Battle Frontier wasn't enough after all. Every day it's looking like Alola will end up being like the Orange League
Besides he couldn't be a 'proper' champion and still travel, sure Diantha and Lance have jobs and Steven has a hobby but they return to their home regions to battle challengers and defend their title the proof is practically there itself. They don't go full on adventuring, and with how many Leagues occur within the span of a single year... Ash wouldn't make much progress lol
Bringing the Champion League back up and letting Ash compete(After he beats the Galar challenge) would be pretty nice, Ash wouldn't be a champion as well... Galar would already have one(Hopefully anyways, it's obvious Alola didn't because of the whole gen 1/anniversary thing. Being the first champion was cool and all, but having an established champion made it more exciting to reach that point of the game so you can beat them! And there's no reason the 'title challengers' can't come back, actually acknowledge that you won and have the old champion come back along with others). Ash would have to beat him/her to be the Champion, but being Champion isn't a requirement for the Champion League according to what was said... winning an official Pokemon League is enough, and
those require *gasp* requirements to enter!
Anyways, gen 9 could then be home of the mysterious Champion League thing and while Ash is doing that he plays mentor to the Pokegirl whose battling the Gym Leaders/Masters/Whatevers of that region. Ash is still around and can play with the new fancy toys and Pokemons, while giving the Pokegirl a goal that's yet to be done for them. Alder proved powerful trainers can still be idiots and a bit silly so there's nothing forcing Ash to suddenly end up pulling a 180 again and acting like he did in XY. Being powerful doesn't mean you have to stop having personality, regardless of what "Smart Ash" fics tell you