It’s called entropy, and it applies to everything. If you’re a pianist and don’t practice on a regular basis you don’t stay the same, you get worse, and it takes extra discipline, effort, and dedication to get better.
Natural selection is a buffer against decay that is constantly operating in nature. Natural selection throws out bad stuff in a competitive environment but has no creative powers. Since decay is the norm, and random errors, statistically speaking, essentially always result in decay, a creature living underground will lose its eyes because the informational cost of producing eyes is high.
Thus, a crippled, decayed creature in a pathologically hostile environment will have a survival advantage. This is devolution, not evolution.
This phenomenon is not only logically obvious, but Michael Behe and others have demonstrated that such is empirically the case.
Belief in the infinitely creative powers of natural selection is illogical, empirically falsified, and essentially represents, in my view, a cult-like mindset.
When evidence of decay is presented as evidence of progress, one must wonder what is going on in the minds of such people.