The awesome power of infallible definition is used sparingly, mainly for the painful yet necessary task of purging heretics. One must accept the virgin birth and resurrection to be considered Catholic, but it has not yet been deemed necessary to cast evolutionists from the Arc of Salvation. Perhaps declaring macro-evolution to be anathema would have spared us the aberration of Vatican II.
Unfortunately, creationists do not seem to be receiving the same consideration. Catholic publications, programs, and public figures are at war against them.
Also you are looking at this problem from the wrong end. The issue here is not "evolution" but the facticity of the Biblical narrative, howsoever much that narrative violates the rules of nature. There is absolutely no reason whatsoever to shunt science aside when it comes to the virgin birth while rejecting creationism because of what science says. All miracles are equally "impossible." Yet Genesis 1-11 is routinely treated as if the events it describes are uniquely impossible in a way no other miracles are.