Throughout his entire life Itachi has failed numerous times.
1. Itachi killed his entire clan to prevent the Ninja War but it still happened.
2. Itachi wanted to make Sasuke a hero but he failed because Sasuke turned into a criminal. He killed a future kage, hijacked a Kage Summit, and joined with akatsuki to capture B.
3. Stopped the Edo Tensei but Madara is still on Earth.
Itachi messed up his entire life i thought he was suppose to be on Kage level he even managed to mess up more than Minato XD.
Well Itachi did indeed admit to being a failure but I'm going to discredit some of your points.
1. The ongoing war has nothing to do with the war that Itachi prevented .. I'm sure this is obvious but if you don't get it I'll explain it.. The war Itachi prevented would have been the Leaf most likely by itself against other villages trying to take advantage at the leaf being weakened if they battled Uchiha.. the ongoing war is the combined and unified effort of everyone against Obito Uchiha and Madara Uchiha who want to create a genjutsu world.. do you see anything that relates these two? I don't think so.
2. You can blame that on Obito for telling Sasuke the truth and influencing him to do all of this..
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If Obito didn't interfere Sasuke would've been thought of as a hero.
3. Well this is Madara after all so I can't blame him although he at least succeeded in stopping edo tensei... besides Madara may have been revived later on.