Re: Why is bleach so terrible?
Well people's opinions on manga are obviously subjected to the experiences they have with each one, however who are you to say what manga is terrible? I personally enjoy watching Bleach just as much as Naruto and am, depending on the previous chapter's conclusion, just as excited for Bleach as I am for Naruto. The fact they are both released around the same time help too.
Regarding the particular volume you read. Volume 21, if I'm not mistaken, is around the same time Ishida gets his powers back and was a relatively quiet point in the manga. Most of the enjoying moments that I find are during conflicts. In fact the most recent arc of Bleach, the Thousand Year Blood War arc, has been the most entertaining so far and in my opinion has seen better fights then most of the battles I've seen in the whole Naruto Ninja War currently underway (excluding Madara's and Tobi's fights).
Anyway, what I'm trying to say is that:
What makes you the judge of what manga / anime is terrible? Different people like different things.
The Volume you mentioned in OP was a quiet point in the Bleach manga.
Bleach's most current arc has seen better action then most of the current Naruto Ninja War.
Also remember, I enjoy both Naruto and Bleach equally.