You can shit on Bleach as much as you want, but the Soul Society arc was some of the best material shonen manga has ever seen (no hyperbole) because of the interesting, easy to understand power hierarchy (captains, lieutenants, and divisions), unique and interesting power-ups in shikai and bankai, a great sub-story with Aizen's "murder" that ended up eclipsing the save Rukia plot, an amazing cast of characters... it really had everything going for it. It even set up the series for further greatness by not revealing every captain's fighting ability, dropping plot hints here and there (Urahara), and, of course, Aizen's grand exit with two of the coolest captains from that arc.
The main problem with Hueco Mundo is that it felt like Soul Society 2.0. Replace Rukia with Orihime, and the Shinigami with Arrancar, and that's it. The Arrancar were also far less interesting because, for the most part, they were monster-like and blatantly evil, and didn't have the same human sensibilities that the Gotei 13 did. There was also no real sub-plot or drama like there was in Soul Society, except for maybe Nel, and that's really grasping at straws. I don't understand how Kubo dropped the ball so hard after setting up such a great premise. Even when the Shinigami enter the picture again in Fake Karakura Town, it didn't manage to reach anywhere near the same highs that SS did because it felt like the battles were artificially set up. In SS, people fought each other for various reasons, at various places, whereas in Fake Karakura Town everyone was matched up to a foe like it was a pro wrestling tournament, and fought in this huge arena. The only time the series managed to get anywhere close to it again was when the arc had just begun and showed potential with the Vizard (who ended up essentially being itsnothing.gif outside of training Ichigo) and their flashback arc, as that once again focused on the drama within Soul Society and touched upon mysteries from the beginning of the series, such as Urahara's tenure as a captain. Turn Back the Pendulum was a really nice breath of fresh air in this regard, as it was one of the few times that it felt as if Kubo was doing some intricate world building.
Seriously, though, the Gotei 13 are still some of the most badass group of shonen characters around, even if they aren't written to anywhere near their full potential.
Edit: Isshin flashback was alright, too, even if Ichigo's mom being a Quincy was kind of contrived.
