Your question as asked has lots of reasonable answers, such as the fact humans aren't all that intelligent on average, and certainly not some asymptotic limit we're aiming for.
I'm sure that it's here to stay, only that it will become much less valuable in the near future. Just like how the .com bubble popping didn't cause the Internet to disappear, the ML bubble popping will not cause machine learning to go away. Instead, it will make it something ubiquitous that gets used with very little thought, removing most of the specialized job market for it.