I agree, there's nothing wrong with Ash acting like a doofy kid, just as long as it's done in moderation, but yeah undoing the progress he made in XY would be annoying.
And its not like Ash hasn't had his doofy moments in XY. I've said it a bunch in the XY thread, but the series has a LOT of shonen elements. Ash especially feels like a pretty standard Shonen hero.
Honestly, I feel like I would have been unsure of the new season initially simply because XY turned out so good, but the VERY different premiss and the character design have left me more unsure than I was expecting.