Couple of thoughts:

You are assuming that a pure function has access to some source of randomness. I think that's a bit less than pure unless a source of randomness is one of the inputs. Doesn't change your point at all, but it distracted me from what you were saying.

Speaking as someone who has occasionally invented new things, I think you underestimate the variety of outputs that can arise from a lifetime of accumulated experiential cruft and a situational fitting function (e.g. "we need a working teleporter to stay competitive"), without bringing in randomness at all.