The Ame No Habakiri is the only blade that will put Orochi down for good. I said this in the past, Oda doesn't reward mere vengeance. If retribution is meant to be carried out, there should be an extra layer to it. When Kyros defeated Diamante, he didn't just avenge the death of his wife, but saved his daughter who is still around. The malice of revenge was overshadowed by the noble act of rescuing/protecting. I think that's how Orochi will be defeated. Someone who wields the Ame No Habakiri slays him once and for all while trying to rescue Hiyori, and not because they want Orochi dead. Because Orochi does not matter in the end.
I'm happy to see G5 isn't the auto win condition we thought it would be. Luffy still has an uphill battle before him. The emphasized importance of haki also goes a long way at not diminishing Luffy's efforts by attributing it all to his "ridiculous" fruit. A devil fruit is a shortcut to power, but you will never realize your full potential unless you have the innate drive to reach it. Will Power is what reflects true strength in One Piece and it's what has brought Luffy this far. The devil fruit was but a bonus at best.