“The best way to predict the future is to create it.” is optimistic. It asserts that we have agency. The pessimistic argument seems to say we don't have agency

“The best way to predict the future is to create it.” is optimistic. It asserts that we have agency. The pessimistic argument seems to say we don't have agency. It follows from this attitude that we can only stave off a collapse. It is one self-fulfilling prophecy against another. Presumably these attitudes are based on more fundamental philosophies. There may be other philosophies with prophetic power than these two.