Just as how I feel about BW as a whole, this league would have been fine if it was a brand new rookie protagonist competing. The loss to Cameron would have stung less considering he was gifted this lineup of fully-evolved powerhouses. However, it was a punch in the face to the fandom, and no respect to the protagonist, by having Ash, who went down taking out a Darkrai and a Latios in Sinnoh, jobbing to a literal idiot of a trainer who only had 5 Pokemon.
This would have been totally impossible, but I wish they had recontextualized Ash's loss to Cameron. Convey it that Ash is now on the receiving end of a DEM evolutionary power boost, and the loss itself was a true upset. Maybe a quick flashback to Ash vs Mandi match at Indigo Plateau, where Mandi, one of the pre-tourney favorites, got upset thanks to Krabby evolving to Kingler and going beast mode. They should have had Ash be saddened by the loss, but make it so that he learns that not every outcome in life is a step forward, but rather sometimes he needs to go a step backward in order to move two steps forward later. This could have been a good foreshadowing for XY, where he refocuses, and decides to train only 5 new captures as to not dilute his efforts among 9 new captures like in BW.