Someone pressed the reset button again.
This is a terrible fucking insult to those who invested time on watching this anime. Not only they made Ash lose once again, but his childish looks and personality seem to be back as well.
This will not end well.

Don't judge what you haven't seen yet.
The school Ash could be going to is to learn of Alola's mysteries. Surely the writers aren't dumb enough to make him relearn the basics of battling and such.
Ash might appear better in the anime than on that promotional artwork.