Just because it cannot guarantee to accomplish this 100%, is no reason to abandon the method and go backwards, basing our decisions on anecdotal evidence and superstition.
The scientific method is still superior to what preceded it and until a better method of drawing conclusions comes along, it makes sense to use it and try to improve upon it.
The true scientific method is more often than not concerned with science' effect on humans, not the universe as a whole. I love science and double-blind experiments, etc. But not particularly humanistic science. :-))