insanely involved with manipulation of wavelengths of light vs just getting bigger or growing more claws or something similarly simple, biologically speaking.

Nature did. That's how speciation works. We're just focusing on the shiny beetles because they grab our attention and the big dung beetles with big horns don't.

Also, as far as evolution is concerned? There's nothing insane about it, they're all equally simple. You're thinking of it from the perspective of industrialisation, and how tough it would be for us to manufacture such materials. That's not the viewpoint evolution cares about, if it can be grown it obviously isn't difficult to do.

How do these processes which use quantum mechanics and wild optical physics become an innate part of nature to begin with.

There are no quantum mechanics involved. And the physics are not wild, they're the basic laws of physics. It's only humans that assign difficulty and exoticness to these mechanisms because our technology base is incapable of reproducing it easily.