You cannot really say it's average since animation is top notch, soundtrack is really good, it just seems that you are over 15 and want perhaps something more than shounen? And with the amount of episodes that show has, do not expect characters other than main ones to be really developed. If you want something with character development then HxH, One Piece, Naruto or Bleach. It might be sad but mangaka just had to throw in a bunch of characters in show setting because it's school. When it comes to one piece with devil fruits, some characters are simply just to OP. Like Oda just finds out of nowhere new uses of superpower that sometimes logically have little sense. And he quickly got to the barrier when you cannot really feel that someone is stronger, because luffy struggels with 50kk bounties same as with 300-400kk, and on top of that everyone just started using haki, when 2 years before a couple of characters possesed such a skill. Btw. you have to keep in mind that characters in show are just sth like 15? Don't expect them to experts in everything, and I feel like Mirko is really blant. he is just a charismatic guy saying "oh i will save everyone" and stuff like that. It's just like mangaka would have a small bar that he uses to create character and he just shifted it towards 100% positivity.