The theory of "irreducible complexity" has nothing to do with an inability to explain how a feature came to be -- it is based on the fact, wholly supported by science, that if (for example) you change even 0.1% of the "ingredients" in a human eye, what you are left with no longer functions as an eye.
Ironically, Steven Jay Gould himself was driven to abandon his earlier notions of gradual evolution because even he couldn't quite explain how a human eye could have evolved if 99.9% of an eye couldn't see, how a mosquito wing could have evolved if 99.9% of a wing wouldn't lift it off the ground, etc. He came up with his theory of "punctuated equilibrium," which states that individual elements in an organism evolve in their entirety. Interestingly, it should be pointed out that there is no more evidence of "punctuated equilibrium" than there was of Darwin's "pure" evolution.