Why are you guys acting like he can't improve in all of those areas you listed? Do you really think he won't grow as a character and trainer for the rest of PM2019's run? Just because he is inexperienced as battles now doesn't mean he will stay that way
I disagree that it was an easy league win but that's besides the point. The fact that the companions entered the league showed that they had no issues with them being involved in Ash's goal. If it happened once it can happen again with Go
And he can't become better as a trainer and work more with his Pokemon? He and Raboot came become stronger together which may lead him to want to enter the WC himself.
He can still fight trainers and catch Pokemon