Haki is, BY FAR, the worst thing Oda has ever introduced in this story.
Worse than Oden.
The way he intentionally dont "fully explains" it so he can justify all the asspullin and retcons in its functionalities.
At least Togashi is sincere with his asspullings.
"Yo, see all these Nen categories? See how each of them work? Ok. There's a special one. What it does? Anything. Literally. If it doesnt fit the other 5, than its this one. When I create some weird ass abilities that wouldnt fit any of the other 5, you at least know there's this special category, so it doesnt seen out of nowhere".
Franky vs Sasaki is gonna be the best fight.
No Haki involved. Just sheer power vs inventions.
Fuck this convoluted ass trash power system.