The question is not whether they fit your definition of Christianity, or what you think they should or should not do, but whether they are, as you so casually lump them, Satanists. I think most of them are crackpots (though mostly harmless ones), but I also do not think that makes them Satanists. There is a considerable resemblance of Anthroposophy to Gnosticism, though they adamantly reject the notion, and experts on Gnosticism consider it morre a resemblance than substance (now is not the time to get into Gnosticism, I think) but they certainly claim to be Christian, whatever you may think about them, and they most certainly do not worship Satan.
I should point out that I did not include Blavatsky, but her follower Annie Besant, who explicitly claimed (whatever you may think) that Christianity fit with her ideas. Whatever qualifications you apply to count someone as Christian, failure to qualify does not automatically make you a Satanist any more than failure to be a Muslim makes everyone else a Jew.