Verification is important, but I think you're omitting from your imagination a real and large category of people who have a basic familiarity with spreadsheets and computers, so are able to understand a potential solution and see whether it makes sense, but who do not have the ability to quickly come up with it themselves.

In language it's the difference between receptive and productive vocabulary: there are words which you understand but which you would never say or write because they're part of your receptive, but not productive knowledge.

There are times when this will go wrong, because the LLM will can produce something plausible but incorrect and such a person will fail to spot it. And of course if you blindly trust it with something you're not actually capable of (or willing to) check then you will also get bad results.