It still makes no sense. No matter how good any shinigami is, it still violates what Aizen himself said and why he created the arrancars.

That is the 4 basic fighting style, Deamon Magic (Kido), martial arts (bare fists), sword style and I can't remember the last one. No matter how one masters all 4 of the fighting ways, there's always a limit. The only way to pass the limit is to release the border between hollow and shinigami. Eliminating the suppressing  energy which limits one's fighting ability.

Arrancars and Viazards are supposed to be released of those limits while captain class Shinigami still bound to those limits.

then in the end, urahara is the real bad ass. when aizen almost defeated by "someone" and later urahara revealed that he is the mastermind for everything . even aizen is his puppet doll, not bad this plot twist.

ichigo said that a bankai cant be so weak to be stopped by another bankai.thats mean gin actually have something under his sleeves?

Aizen grinned, "Since when you thought that you were blowing me?"
Everyone shocked, and noticed that Urahara was actually blowing Gin!!