The aircraft carriers were the shortest of the bunch. They had at most two floors, but this didn't mean that they were small. They were short, but they were wide. What they lacked in height, they made up for with width and surface area.
Their short and wide structure was designed so that they would be able to act as a mobile airfield. Even before the aircraft on them were deployed, their small size didn't diminish how imposing they were.
But as big and imposing as all these mobile fortresses and carriers were, they still looked small compared to the size of the walls. After all, the tallest of them was only 100 meters in height while the walls were a kilometer tall.
The Red and Blue Fire sect had other types of equipment that they used to invade worlds and bring them down, like their floating fortresses, but they couldn't use those here because of the arrangements of the walls.
