reasons: too many DAM FILLERS in the wrong place at the wrong time
sometimes they interupt the CANON story(and that is a big NO NO)
too many minor/yet major screw ups potentially
couldve progressed very likeable characters storylines like

anko hayate hyuga /dead sound ninja/
screwed over characters too often for magical moments to make the good guys win
too much non interesting GO Back To moments
Jiraiya died too soon
Pein being Jiraiya's student came out of nowhere
Konan/Shikaku knowing Kamui's weakness(without really being explained)
Too Much repetition/ copycats = used to be everyone was alot different before shippuden
needed Kakashi's Rampage
too many forgotten story aspects for what people looked forward to