Doflamingo had a more impressive feat. Dressrosa is significantly larger than Onigashima, and his Bird Cage spanned the entire country. It required him to be conscious to operate, but it was otherwise able to continue independently of him.
In my defense, I haven't really had the experience of debating Nat on One Piece (outside of profile posts). I mainly stay away from the Admirals vs Yonkou threads.
The doflamingo cage is an automatic skill programmed to close, (close the cage).
KAIDO is a ZOAN, it was said in an SBS that he does not fly, he walks on the clouds that he generates, in a nutshell he floats in the air, thanks to the nuves, generating clouds and putting his paws on them, that is not enough, kaido didn’t generate the nuves and glued the island on top of it to float, he used an amount of HAX (gravitational or force) to dig the island out of the ground, an absurd amount (just creating the nuves and more nuves is not enough because you need to put the island on top of them), continuing, with the clouds around, to break its solid base, with the island resting in the clouds, notice that the island cannot fly it floats thanks to the clouds, the clouds do not go where you want to randomly / automatically, kaido has full control over the fluctuation of the island and needs to control it to walk, maintaining the gravitational level necessary to keep the island hundreds of meters in the air and in motion.
The moment you use some skill in your DF you are wasting energy, however small, LAW when using the ROOM, Doflamingo was almost knocked out by Luffy and the cage stopped, but she was still there, this is the living proof of that the skill needs the user with strength + energy, if KAIDO is knocked out the skill loses strength and the island falls, this means that the skill is not doing everything, it is literally intertwined with the condition of the caster.
In short, KAIDO has already used an enormous amount of energy, which is classified as an island level, generating a skill so great that it is capable of sustaining the island for a few hundred meters in the air, not only that, but the ability it generates it is so strong that his strength is able to dig up the island from the ground and break its base / roots.