User blog comment:Miskos3/Fairy Tail 536: The Flame of the Dragon's Roar, Review/@comment-68.33.90.75-20170520191729/@comment-24489996-20170521194621

It's favoritism, but not in the way you're thinking; it's emphasized before on his twitter and during the Afterword of some of the volumes that he writes FT for the fans, thus many scenes throughout the manga pander to the shipping fanbase.

Thus, some characters who are either insanely powerful, quick-witted, or well-equipped for combat are tossed aside during fights, treating them as weaklings while favoring other characters that either "play a major role" or "part of the main cast".

The Spriggans are the embodiment of this to a T. They're lauded as the most powerful mages in the entire FT world, and most were treated worse than the Alvarez fodder; only one or two got proper fights, but even then it was a disgrace later on when they fought again. Sadly God Serena, Wahl, Bradman, and Ajeel are prime examples, given how each one was easily defeated by enemies they could easily trounce.