François Chollet made an interesting geometric analogy on Twitter. We tend to view Intelligence as something unbounded, like the height of a pole. But it could be something closer to the roundness of a polished sphere. Once close to the limit, incremental improvements are less and less significant.
The intuition we have about the nature of cognition and its whole shape and limits is almost entirely built by looking at ourselves and our peers, comparing that to an ant. I feel this is largely naive and misguided.