I think that historical Satanism as it appears in literature can give very interesting insights into undermining Christian civilization by embracing the sensual and independent reality that Christian dogma represses.
Some literary or even cinematic forms of Satanism are truly dark and morbid, others are an interesting quest for self empowerment. But the typical modern Satanist, who listens to black metal and prolongs shock value that most people grew out of when they were 21 is a caricature of what true Satanism, the kind that none of us would ever hear about or be exposed to would be like (and I realize I am being simplistic in this example).
I think the analysis is simple. What are the major elements in modern Satanism? Most Satanists we encounter, on the web or in real life, for the most part are Satanists by virtue of popular culture. They began by inspiration of music or other themes in popular culture, they largely have superficial knowledge of historical occult, late medieval occult literature, or ancient religions. In a way modern Satanism is like a reconstructionist neopagan belief system, a Biblical antagonist, or other ancient antagonist (Set, or even Ahriman) is taken and serves as the personification of a superficial unrestrained alternative to mainstream (usually Christian orientated) society.
If true Satanists exist. I always envisioned them as having a tasteful appreciation of classical music, shrewd understanding of history and the powers at play, minimalist taste in art as opposed to 'evil' Satanic imagery of skulls and demons.
So Satanists may be out there. But I think they are preoccupied with more refined interests.
None of this, however, means that various people who may adhere to a 'dark' path, Satanism, the Temple of Set, etc. are not serious in their world view, or the way they choose to live their life. They just never strike me as individuals who truly embraced the essence of a higher culture of 'Satanism', or as people who achieved an impressive level of independence and power.