First, what Bleach did great: Action. The series really have very good fights and the actions scenes, even for a manga, is great.

Kubo's art is very good, despite being very noticeable he don't have much variety. Mostly of the female characters are too much alike, with just the hair and breast size different.

Now, the worst part: the story. At first, the story start very good. With a lot plot twist, some mysteries during the first arcs and the Arrancar arc ends. To be fair, that was a very good finale to this manga, in my opinion it was perfect, and I would give 6/10 here... but they continued with the FullBright Arc and Quincy arc.
The Fullbright arc looks like a filler. It have no purpose at all, but being used as a McGuffin to the next arc.
The Quincy arc really started very well with a sense of despair and because this was supposed to be the last arc I really was hoping that everything was possible...nah! This arc ends with plot holes, unresolved issues and a lot Deus ex Machina.

And the characters...well, Kubo really like to create a bunch of characters. The problem? They are just that, a bunch of characters. A lot of them have zero characterization, or are definite by a quirky or a gag.
The worst really go to Ichigo's friends who have no power at all. They really like very interesting characters, but because they have no super powers they never have a character development and some are even disappear "mysteriously" like Ikumi or Ryo.
This is a real problem with a story with a lot characters and sadly Kubo didn't knew how to deal with this.

I like to say Bleach is like Transformers, it has cool fight scenes and sexy ladies...and that. The last 2 arcs really damaged the plot and characters.