Their argument consists of implying that lifting an island is much more difficult than lifting a city.
I personally disagree, since this is just a standard notion. The sizes shall be compared before judging. I don't see a mammoth-like difference personally.
It's not whether Fuji can do it or not... Maybe he can
The point is... Fuji did NOT LIFT a city/island... he lift a RUBBLE of a city/island....
Kaido lifted the ENTIRITY of an island/city with all its ground/underground/roots that falls deep inside the water....
This is basically the difference... and Onigashima when we first visited the island, we got a massive widspread about how gigantic EACH and EVERY thing in it... it's a MUCH MORE MASSIVE island than Dressrosa... for sure just by seeing one of the mountain compared to the SHIPS of the allies..
So, again... Fujitora ability SHOULD BE able to pull it off... but featwise, what he did is on a SMALLER scale than what Kaido did... that's all
Also, the method is different in that, Fujitora's fruit itself SHOULD allow him to apply or negate gravity/weight on specific zones.. So, his FRUIT should be the fruit to pull that shit off
While Kaido's method is that he "creates a flaming cloud" in order for him to fly on it.... kinda like Momonosuke.... now, I don't know about you, but it seems like a secondary ability "not the main ability of the fruit" and ALSO, it seems like it SHOULD BE an ability that is AFFECTED by weight...
for example, The more weight, the harder to walk on those clouds and not fall.... At least that's what it seems to me...
So the point is that:
1- Kaido is doing it on a MUCH LARGER SCALE while the ability being "SECONDARY" not the main feature of fruit.
2- Kaido's method of doing it "SHOULD BE MORE TAXING" on Kaido... compared to Fuji... YET they both did it effortlessly I daresay...
Those two points makes it that Kaido's feat is much more impressive
And yet again, I'm not saying Fuji cannot pull that shit off.. he might be able to... and who knows, effortlessly TOO...