Two DFs being important to Rocks’s plan doesn’t mean they are the only ways to hurt Imu
It heavily implies that those are the only ways to beat Imu based on Rocks´s statements, but it´s not an outright confirmation. The fact that Oda didn´t have him say anything about training Haki, getting Harald to train his haki, nor his subordinates tells us enough, sometimes the omission of something is more than enough.
Especially if he isn’t even using his true body. Each of the 5 gorosei can potentially be a puppet of Imu’s, and in fact Luffy is already fighting one of Imu’s puppets now with Gunko before the final war.
Rocks wanted to defeat Imu entirely, not just one of his puppets.
Despite what people have headcanon´d themselves into believing, Imu´s vessals have never been stated to be like, 5 tiers below him.
Yes, Luffy is fighting Gunkimu, with the help of Loki, who has one of the 2 fruits.
They are part of the worst generation, they are built up to surpass the previous generations. They are in their early 20s and already beat a yonko and earned 3 billion berry bounties.
Consider the gap between Dressrosa Law and end of Wano Law. They could likely grow just as much, if not more by the finale.
Nah, The majority of the worstgeneration won´t be surpassing anyone, they´re just the most chaotic. Oda wasn´t even comfortable having Kidd or Law win 1v1´s against Big Mom for a reason.
They can double or even tripple in strength, and they´re not suddenly going to have haki that scales above 5 ACOC users, and even if they did, Oda is only really implying you can fight Imu with special DFs, so it doesn´t even matter.