Here is an example provided by a member in the "Evolution of Creationism" thread. The person quotes a section of Darwins Origin of Species.
In the Articulata we can commence a series with an optic nerve merely coated with pigment, and without any other mechanism; and from this low stage, numerous gradations of structure, branching off in two fundamentally different lines, can be shown to exist, until we reach a moderately high stage of perfection. . . With these facts, here far too briefly and imperfectly given, which show that there is much graduated diversity in the eyes of living crustaceans, and bearing in mind how small the number of living animals is in proportion to those which have become extinct, I can see no very great difficulty (not more than in the case of many other structures) in believing that natural selection has converted the simple apparatus of an optic nerve merely coated with pigment and invested by transparent membrane, into an optical instrument as perfect as is possessed by any member of the great Articulate class.
What the poster fails to mention is that Darwin failed to discover an evolutionary pathway used to make the eye. Instead, he pointed to modern day animals with different kinds of eyes and suggested that evolution of the human eye MIGHT have involved similar organs as intermediates. At best, Darwin convinced most of the world that a modern eye evolved gradually from a simple structure, but he didnt even try to explain where the starting point - The light sensitive spot - came from.
When it became apparent that larger complex features could be explained by extant and extinct species (the mammalian middle ear is another good example) the creationists moved to systems which could not leave a fossil record, namely cellular microscopic systems such as bacterial flagellum. With zero chance of a fossil record they wouldn't have to worry about those pesky transitional fossils.
Larger complex features cannot be explained by extant and extinct species. To say that it "could", is a rather weak hypothesis. Saying something "could" have developed in a particular manner isnt the same as providing viable, scientific evidence that it has. This is the problem with societies main stream view of evolutionary science. Possibilities and educated guesses get presented as irrefutable fact.