What is human intelligence, if not the result of a colossal, distributed function optimisation process driven by evolutionary forces over millions of years?

true, it's the result of an optimization process, but intelligence itself (whatever it is...it's a suitcase-term) isn't as simple as that. Or maybe it is, I don't know!

"Optimization" describes the result, not the implementation. Unless you consider intelligence to be average-suboptimal, it's entirely reasonable to say that it's about optimization without committing you to any claim about how intelligence is implemented.