"Scientism" has two distinct definitions.
One is defined by some as an "excessive belief in the power of scientific knowledge and techniques."
So this clearly depends on the meaning of "excessive". If all that science does is verifiable and yields new insights that create new technologies, then it should not be considered excessive, but "realistic".
The term "excessive" should be relegated to the realm of science fiction. Of course there are the whacked out "scientists" who profess crazy ideas outside the mainstream of factual science (i.e. absolute truths, don't get me started again, re: nukes). You can throw them all in with the derogative term.
From wiki's secondary definition (This is its use in the above treatment of the word) :
"The term Scientism is generally used critically, implying a cosmetic application of science in unwarranted situations considered not amenable to application of the scientific method or similar scientific standards. "
Wiki's primary definition :
"Scientism is the promotion of science as the best or only objective means by which society should determine normative and epistemological* values."
(* relating to the theory of knowledge, especially with regard to its methods, validity, and scope, and the distinction between justified belief and opinion.)
Depending on one's definition, Scientism works for palmists, card readers, etc. They should not be included in the definition of "methods, validity, and scope, and the distinction between justified belief and opinion."
There are clearly two distinct definitions which must be clarified before one can accept any rational aspects for its use. But this might not sit well with those wanting to distort the real meaning of science.
There already exists a great term that most people recognize and use on a daily basis that best describes its methods, validity, and scope, and the distinction between justified belief and opinion. That definition is called simply "science", and for those of us where it really matters, it needs no definition.
It is its own definition.