Falsificationism has always been an important part of science. Many scientists argue that if a theory cannot be falsified, then it does not qualify as genuine science. That view may be overly simplistic—and it is not falsifiable by the way—but certainly falsificationism is an important tradition within science. Theories are based on empirical data, and it is the empirical data which should have the final say on whether the theory makes sense. Therefore it is curious that evolutionists, while insisting on falsificationism for theories they oppose, suddenly drop this favorite criterion when it comes to their own theory.
One of evolutionist’s favorite defenses against criticism of their theory is that mere criticism is insufficient. Criticism, they say, is nothing more than a negative argument. What is required, they say, is a replacement theory. So evolutionists, who when looking outward favor falsificationism as much as anyone, later deem it to be insufficient when the spotlight is turned onto their own theory.
When Darwin proposed his theory he asked for a fair-minded analysis. Compare the theory with the evidence. If the evidence does not support the theory, then it should be dropped. That is no longer the position of many leading evolutionists who reject any such analysis as insufficient.
This may be because evolution is, itself, a negative argument. Evolution is, and always has been, motivated by failures of creationism and design. If god did not design or create this world, then it must have evolved. Somehow. Evolutionists perform research to try to figure out how evolution could have happened, but it must have happened—that much they know. That is a metaphysical position, not a scientific position, based on a negative argument. It is not falsifiable.