the reason that kishi never put him against a strong opponent was because in a way itachi was always a good guy. think about it, early on he had a chance to kill kakashi, guy, asuma and kurenai but he didnt, chose to spare sasuke and even let him kill him, had many an opportunity to kill naruto but he didnt.Itachi was able to talk the talk and walk the walk he just chose not to. It was never itatchis place to square off against beast opponents, but you do forget that he did take down a couple of perfect jinchurikis.
the jiraiya pein fight was meant to b dramatic because it was student vs master and the reason jiraiya had liitle knowledge against him was because he left nagato at an early age.
there was never any need for kishi to put itachi into an epic battle to the death, his role was to b a secret hero until the very end