^Honestly, Naruto not being able to take on 5 Bijuu (now) would be a little unrealistic to me. I mean, characters like the dead Raikage could defeat the Hachibi by himself, and then you have Madara and Hashirama who can both defeat the Kyuubi (in Hashirama's part, by himself while fighting Madara (presumably)). So, Naruto using the full power of the Kyuubi should be awe-inspiring and should be doing exactly what we have seen.
Then again, I felt Kishimoto underpowered Naruto during the initial Jinchuuriki exchange.
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