User blog comment:Hollow Mario/Worst Filler and Original arc/@comment-5398287-20150109004655

Invasion Arc really has no equals when it comes to awfulness. You can make cases for how the Bount Arc went on for too long and had wonky animation, how the Amagai arc introduced a completely one-dimensional, annoying character (Rurichiyo) who kept hogging the spotlight, and how the Zanpakuto arc had an OP villain (Koga) and made some of the canon characters (the spirits) kinda silly, but the Invasion arc managed to combine all of those problems and more in one 25-episode long "let's ignore everything canon about Bleach in order to focus on a Mary Sue who replaced two of the most popular female characters"-fest with a villain whose Zanpakuto was more OP than Aizen and whose "army" was literally the most unoriginal possible idea in fiction.

It's really no wonder the anime was cancelled when the studio had fallen to that abysmal level of filler after the other halfway-decent arcs they made.