I feel like the OP is more asking an honest question about how evolution works here, not that he’s necessarily just trying to rehash debunked anti-evolution arguments. The problem, as I see it, is that there’s a lot of parts about evolution that don’t really work in an intuitive way, particularly for people that aren’t scientists. I can absolutely see why the evolution of the eye would seem like a tall order, because it used to seem just that way to me.
First, I think the biggest problem is that evolution isn’t straight up random. I think the intuitive idea of how evolution works is generally more along the lines of like a guess and check. It still works using random processes, but the actual way it works out is remarkably more efficient. The best intuitive example I can give would be like playing a game of guessing the secret number between, say, 1 and 1000. People think it’s just like “is it 7? No. Is it 513? No…” Obviously, that’s remarkably inefficient. Rather, it’s a lot more like “Is it higher or lower than 7? Higher. Is it higher or lower than 513? Lower…” It’s not perfectly efficient, bisecting it would be the best, but a random division isn’t bad. It’s not a perfect analogy, but hopefully at least the idea that it’s not just equivalent to guess and check is there.
Second, I think our intuitive understand of the timescales involved just don’t serve us well. We don’t do well in understanding numbers like millions or billions, but they are much huger numbers than we can meaningfully conceptualize. Further, understanding that while the human reproductive cycle is generally around 20 years or so, the overwhelming majority of life has much shorter reproductive cycles, a few years for many other mammals, and as long as hours or minutes for microbes. So, not only is evolution more efficient per generation than we think, but there’s a whole lot more generations to work with than we intuitively would believe there is.
Thid, as others pointed out, the idea of irreducible complexity, that something realy complex like the eye or ear, is ultimately just an argument from ignorance, the idea that because we can’t think of some intermediate step that may provide an advantage, that it doesn’t exist. With the eye, for instance, others laid out a few examples of useful intermediate steps. Initial light sensitivity is useful, it would help life in the sea locate the surface, which could help with finding and eating photosynthetic microbes, etc.
But beyond that, there’s other factors at work besides just an advantage in reproduction. Sometimes random mutations provide no meaningful survival advantage or possibly even minor disadvantages appear and stick around for other reasons; the only part that really matters is how successfully they reproduce. For instance, particularly with sexual reproduction, there’s a number of species that have characteristics they use to attract mates, like bright and colorful plumage. It may actually make it more difficult for them to hide from predators, but ultimately all that matters is their ability to reach reproductive maturity and pass on their genes.
Or, similarly, sometimes stuff seems like a bad design, like external gonads on human males and we might think that evolution would “fix” such an obvious mistake. But evolution is unlikely to converge on an ideal design, just generally the best that it’s stumbled upon.
Finally, I think the last issue the OP is struggling with is the fallacy of the excluded middle. The idea that it’s either creationism or evolution, and so if some aspect of one is shown to be incorrect, then the other must be true. For fundamentalism, that holds to inerrancy, this seems like a logical way to approach it, because accepting 100% correctness is a tenant of that belief, but that isn’t the case with science. Not only is it possible, but it’s incredibly likely that some aspects of our current understanding of evolution are incorrect, but like evolution itself, we don’t throw out the whole idea, we make small adjustments and try it again. And, even if by some chance we find that a major part of it is completely wrong and the entire theory collapses, the doesn’t make an argument for creationism, as it’s possible there’s some other explanation that could explain all of the current observations plus whatever that new one may be.
And on a more personal level, as a theist myself, raised believing in Biblical inerrancy, I actually found that taking this approach helped strengthen my faith a lot. The idea that an omnimax God, to whom time has no meaning, would create us “perfectly” in a single instant at the begining of time is self-contradictory, but this feels like it fits a lot better with those premises. That’s a discussion for another thread, but I felt it was worth putting out there so the OP doesn’t get the impression that evolution and religion need to be at odds.
