That's why Kaido was desperate for a fruit? That's why Xebec saw two certain fruits as crucial for conquering the world?
Yes, the ceiling for Haki is greater than the ceiling for DFs, but Haki (CoC) is expected at the top, DFs are an extra to move the ceiling.
And yes, there isn't a power creep comparable to Kaguya in Naruto, but Imu is decisively above one Yonko, that was the point of Shanks' concerns who said that Imu's power is incomprehensible.
That's why the Roger pirates waited for Nika's arrival, because they knew their military Power alone isn't enough
Kaido wanted a fruit because his shipmate, Whitebeard, had a fruit also... As I said, it is a cheap way to power.
It is nothing special that allows one to break through human limits. He didnt become god tier after eating it, despite being the strongest 10 years
after eating the fruit...
Blackbeard ate two and still is merely in the realm of old legends... Right after eating 2nd fruit and proclaiming he is the strongest now, it is his era, he backed down against Shanks, the hakiman, saying he aint ready to fight him yet... Despite taking on 2 legends of Marines...
Shanks merely said that Imu's power cannot be measured, dont try to twist this statement. Imu has many things locked inside his Omen locker, it is a fair statement that his power is hard to measure because one doesnt know what he has inside it... There is also the thing with Covenants, which he most likely benefits from and gets stronger from forging as well as the treasure of MJ which he likely can use to further add things to his skillset... That's why his power cannot be measured.
Military power is exactly what is needed, one guy will never achieve anything.
A military power of a single crew was never gonna work against the strongest organization in history.
That is why Nika is turning everyone he meets into his allies, his future military power.
That's why basically all Pirates, Revolutionaries and strongest allied nations like Wano and Elbaf will all join hands to take on the strongest military in the world.
Imu is a jack of all trades, he has yet to prove he is a master of any single one.
For all we know, he may be weaker than present-day Shanks. A guy with haki ability to nullify all Imu's buffs.