How about the jellyfish? It’s highly complex in its feeding mechanism, and highly efficient in motion. Yet it’s method of propulsion is incredibly simple, not complex at all.
Complexity is not required by evolution! A monkey’s tail is considerably more complex than that of the gorilla or human (we both have essentially none - just a few remnant bones), and it serves the needs of the monkey quite well - an animal that is very light.
Likewise a bird’s skeleton. Considerably less dense and complex than a human’s, but that is what allows it to fly.
To say that evolution preferred anything beyond single celled organisms (the required starting point) - that are perfectly efficient over an organism with millions of cells pumping this or that chemical out to regulate the organism or help it eat is such a contradiction that it makes no sense.