I highly, absolutely, stupidly, any adverb you can find, disagree with you on that the manga shouldve ended in Pain arc. By then we had wayyyyyy too many lose ends, and most of us would ***** so hard about it that Kishi would end up becoming the Justin Bieber of mangakas, way too many haters, those who like his work are idiots who cannot analyize or criticize properly to save their lives, if im explaining myself correctly. Plus, some of, like above me some posts have said, enjoyed some of the arcs after Pain (i hated that arc btw, with all the screw up, bullshit, and TnJ on narutos part), for example i really enjoyed Sasuke's character in 5 kage summit arc due to how much you can see he has changed, to me, that arc has been the peak of his character.
I do agree though that the manga has been dragged on too much, which became a little bit too apparent in War arc, i cant say exactly what went wrong bar the asspulls that have been coming since Itachi turned out to be good, but theres definetely some sides of the plot that Kishi didnt handle correctly or just didnt think of them thoroughly.
Btw, theres no perfect manga? FullMetal alchemist, much?