The school was irrelevant though.
Ash didn't rotate Pokemon in Sinnoh. Gible was caught after Gliscor left, and old Pokemon were only used in the Sinnoh League for the purpose of promoting HGSS (which is why most of them were from Gen 2).
Pokemon anime series usually have around 140 episodes, give or take.
Unlike past regions, Galar will be sharing screentime with seven other regions. There's not gonna be any time to flesh out Galar or give it proper focus.
And the people who are only interested in Galar will have no idea when...
Ash doesn't need to do the badge quest and there's not gonna be time for him to do it anyway without it feeling rushed. It'd basically be back to back gym battles with no journey to back them up or give them context.
A regional champion doesn't need to challenge gyms anymore.
Visiting all the regions isn't gonna give the Galar Gyms and League much breathing room. Whatever they do with Galar will feel extremely rushed and half-baked because it had to share screentime with seven other regions.
It'll just remind us of the fact that we were robbed of a proper Galar journey.