so they can't very well go about having the girls and grown-ups kicking too much ass, it might scar those poor widdle adolescent male minds if the boys aren't the strongest characters even if it makes no sense.

Oh, their poor little male egos wouldn't be able to take it! Oh noes!
*nods*

Honestly, I have read enough GOOD shonen to know what the really frustrating mistakes are due to the mis-steps of the author - NOT innate tropes of the genre.