I mean....Big Mom lol. Either she never used it or was already using it (and Oda just decided to not elaborate).
I don't know what to tell you. 5 chapters prior I would have totally agreed, but the narration of the story is disagreeing with that idea currently. He's been setting up a dramatic climax to the fight, with no allusion that there is anything more beyond what we have.
Do I want to be wrong? Of course. But there's clearly a clock ticking and the climax is aligning with Orochi being defeated, Momo finally controlling the island, the Wano lanterns rising, and their alleged final clash.
If it just...continued beyond this point, then there is no reason for the author to set it up this way in the first place
You summed up why most are feeling a bit bitter about wano.
A four year long arc with Beast pirates and BM as antagonists.
King and queen got done in few chapters.
Jack - damn I don't even wanna start with him. Oda done him dirty plain and simple.
BM - a yonkou was defeated in few chapters without we actually seeing her going all out - using advanced haki or Awakening clearly
And, then you have Luffy vs kaido climax being setup with all those lanterns and luffy with a bigger/stronger punch.
Yet, we are missing out on
Kaido's flashback
Kaido clearly using awakening - zoan awakening in an arc which started with smiles and how kaido wanted an army of zoan DFS user
Also, there is no dawn in wano right now.
That's why people are feeling conflicted.
And, to me a fire attack in G5 would have been perfect.
Kaido is vulnerable to fire
Oden was boiled alive
Everyone waiting for the dawn
Fire signifies sun and rise of the sun signifies dawn and Luffy is symbolic to the Sun.
With all these remain being addressed (not to mention zoro reaper plot which came out of nowhere), I don't see this ending of wano being any where near to be a fitting end