I always loved it, but if I'm going Give a honest answer then The beginning of the war was a bit slow, and many fights were off screen. Also Kaguya ruined it a little, I liked Madara more, he got shit done.
When dojutsu became more than eye techniques; Susano'o. (Ninjas come on)
Defintely after the Pain Arc. War Arc was not hyped up correctly, not enough deaths for us to get emotionally attached to it, Naruto was soloing characters left to right, Sasuke reviving Orochimaru to talk with the Kages (really Kishi), the Juubi, Kaguya, and etc.
After pain arc the quality of the Manga dropped, specially when Kaguya showed up and Kishi went insane with the power ups... the end was awesome except for a few pairings and the design of a few childs
*proceeds to hop on amateur critic bandwagon*
Uh yeah when the war started and we saw character development from the main characters and the previous hokage. Definitely not kaguya
There has never been a point in the series where I thought the series was shit from one stage till the end. It has been a rollercoaster ride - ups and downs here and then. But to answer the question, the beginning of the war arc and its ending (when Kaguya was introduced) were the lowest points of the manga. The war arc had its great moments (it has some of my favourite scenes) but it is a shame that it could have been much better written off. It had potential to becoming one of the best arcs of the series but it didn't receive that treatment, unfortunately.