Think of it as not that people can't think, but a long time of not having to use their brains makes the ability atrophy.
And then, when things start to break down, where AI can't make that 'leap', crops fail because they're being nourished with Brawndo instead of water-from-like-the-toilet.
The series “Connections” talks about the “Technology Trap”, man simply won’t understand the technology and what it does. And when it suddenly isn’t available, society will quickly fall apart.
See, I think that’s my biggest fear.
Humans are inherently lazy. If they stop using their skills and their brains and let AI do all the heavy lifting... we devolve.