*** which is answered quite simply, but emotionally unsatisfactorily, ***
Ahhh, there is where the problem comes in: "emotionally unsatisfactory". That is, "I don't want it to go that way, so I won't believe it."
This grows (seems to me) out of teleological thinking--trying to think about where an organism was, in effect, "trying to go". That is a very seductive thought, and hard for many to avoid. Because we are, naturally, interested in "How did the world come to be as it is?" we anchor our thought, as it were, on the present--on the eye that focuses and sees color and works with another eye in binocular fashion, say, assuming that as an immutable, fixed end of the process--and then think about "How did the organism manage to get there?" But of course the organism did not manage, did not choose, did not intend to develop that kind of organ. But to give up that kind of thought is emotionally unsatisfactory, and we don't want to accept anything that doesn't answer the problem the way we set out to ask it.
The organism way back there was not trying to develop the modern eye, nor even a primitive eye. Indeed, it was not trying to do anything except find food and reproduce.