Even if the assertion is correct, what would life be like with computers incomprehensibly smarter and faster thinking than humans?

All management decisions from the top down to individual manual workers handled by an AI (LLM or otherwise)?

Owner has a company-wide AI, instructs it to maximize profit and lets it run. It handles hiring and firing, marker research, advertisement, ordering supplies, ... It generates individualized instructions for each worker what to do throughout the day. Any communication between humans would be redundant, the AI would have microphones and cameras everywhere, humans would only be needed for physical interaction with the world. Even communication with other companies, suppliers and clients, would by done between AIs, they would be better and faster at negotiating.

1) It sounds like a dystopian nightmare - constant surveillance and taking orders from a machine which only cares your productivity.

2) Would it lead to a devolution of the human race? What makes us different from other animals is intelligence. If all humans are good at (= economical to use for) is manual labor, would intelligence stop being a sexually attractive trait?

3) It would completely remove any social mobility. If those who own companies continue owning them after an AI revolution and there's little economic value in human labor except the most menial, then there would be a 2 class society with almost no way for non-owners to become owners.