Uh, no it wasn't. Naruto's rating didn't plummet when it hit filler territory, granted ratings weren't as high when it was following the manga, it still had decent ratings even after Toonami's demise and the series was put on hiatus not because of ratings but due to changes in the network in general, reports show that CN could have gotten Naruto Shippuden quite easily but decided not to.
For the most part they're really not all that terrible, the truly bad ones were the standalone ones (Curry of life, Money-bag jutsu, the fake gai and rock lee) but the arcs themselves were exactly pretty good and gave characters like Hinata some worthwhile development that Kishi didn't. I really have nothing bad to say about the Shippuden fillers since all of them have been good especially by giving Asuma and Jiraiya decent backstories, exploring the character of one of the jinchūriki and more importantly character development that Kishi glossed over. Too bad that everything associated with filler and Naruto are gonna be precieved as bad because of a few REALLY bad apples