What will happen to the body if new conditioned reflexes are not formed?

Since everything is developing and the living world does not stand still, it will be very difficult for organisms if new reflexes are not formed.
Due to constant development, new viruses, parasites, predators, etc., become stronger and smarter, they receive new opportunities for attack, infection and various ways to harm. And if the body does not develop new reflexes for self-preservation, then half of all living will begin to die out.
Reflexes are essential to life on earth, and without them it would be too difficult to survive.