If evolutionary biology could explain a toaster oven, not just a tree, it would be worthless.

But it can, if you consider a toaster to be an embodied meme. Of course, the evolution that applies to toasters is more Lamarckian than Darwinian, but it's still evolution. Toaster designs that have higher utility to human beings lead to higher rates of reproduction, indirectly by human beings. The basic elements of evolution, namely mutation and reproduction, are all there.

What's interesting is that while natural evolution of biological organisms easily gets stuck in local optima, the backwards retina being an example, artificial evolution of technology often does not, due to the human mind being in the reproductive loop. This is, in part, because we can perform local hill-climbing in the design space after a large potential improvement is introduced, much as described in this article on the use of hill climbing in genetic algorithms. For example, we can imagine making the change to the retina to fix its orientation, and then, holding that change in place, search for improvements in the surrounding design space to make it workable, thereby skipping over poorly designed eyes and going straight to a new and better area in the fitness landscape.