What those people actually mean is "I can't wait for AI to be so good that it'll be obvious that it should run all the aspects of our society". The current state is irrelevant, nobody wants to put those in charge.

What are the people thinking who say they can't wait for our society to be run by humans? The most common state of human government capability can't even put human suffering before numbers in a virtual bank account, can't prioritise truth over falsehood, can't restrain themselves from bribery, can't reliably turn up to hearings or ballots, can't organise projects and complete them, can't compromise when millions of people depend on it. We want to dismiss alternatives which haven't even been developed yet for not being good enough?

The argument is that a hypothetical benevolent ASI can't be corrupted like literally all humans can. Those people are likely referring to AI's as they appear in Ian Banks The Culture series.