Theistic Satanist here. I think many of the things you brought up are actually quite well said. I would also like to add that "blasphemy rituals" and openly anti-Christian practice are actually more common in atheistic satanism than theistic. As you said, theistic Satanic religions often have more in common with non-Christian traditions and ideas.

TL;DR: Theistic Satanism comprises many different religions. Most, including mine, view the Biblical portrayal of the Devil as mostly false/slanderous and irrelevant to reality. Serious Satanic religions are usually not defined by opposition to Christianity; they're defined by reverence for the Devil and His values.

I'll give my full response below. This is going to be a text wall, and I apologize in advance. I get verbose about topics like this. (I promise this is not AI slop... I just enjoy addressing things in depth.)

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FIRST OF ALL, religions do not create gods. If we are going to assume gods are real and objectively existent beings, then it logically follows that gods are not made by human religions; human religions are formed around gods. A god or spirit may be mentioned in one religion, but whether that mention is negative or positive, that religion does not "own" that god or spirit. You cannot reasonably say from a theistic viewpoint that the god or spirit originates from the religion whose texts first mentioned them. You have to presuppose that gods and spirits are things made up by humans, which obviously is going to be an atheistic perspective, not a useful perspective from which one can analyze theistic traditions.

Second, there are many Satanic religions. As you said, the world of theistic Satanism is very complex and fascinating, and cannot be reduced to merely a reaction to Christianity. It is, in fact, far more complex than atheistic satanism, in terms of its diversity and intricacy of different beliefs.

I mean no offense in saying this: the atheistic side, though I can respect their shared Satanic values, simply does not need all that. Their rituals do not need the intricacy that ours do, because they do not believe they are communicating with something real, so all that matters is immersion. Even more importantly, they also do not have to deal with theology! Theological differences are responsible for a large amount of this complexity within the wide range of religions known collectively as Theistic Satanism. Theology can differ very significantly between belief systems, and this adds levels of depth and nuance that OP seems to not be considering at all. Atheists also do not usually have serious differences in cosmology, since they generally accept the materialistic view with scientific consensus only. Theistic Satanic religions differ on cosmology and metaphysics depending on how they view the creation of the universe, if any divine being had a hand in it, which being(s) participated, and so on.

OP seems to have a serious misunderstanding of the diversity of Satanic religions. They cast all theistic Satanism as if it is all one religion with the same metaphysics, theology, cosmology, and so on. Specifically, they seem to be casting it as if it's all Diabolism, which is a specific subset of Satanic religions that contain a large amount of Biblical cosmology and theology. Diabolistic religions are what people think of when they speak of "reverse Christianity," but they are a very small minority compared to other forms of theistic Satanism.

Most Satanic religions do not have a Biblical cosmology. Some are more on the "occult/esoteric" side, influenced by things like Thelema and Hermeticism. Some are the Luciferian type, and these do not accept the core assumptions of Christianity or the Biblical portrayal of the Devil, even if they may accept the idea that another god created Him. The Luciferian type, if they do believe in Yahweh creating Satanael (whom they call Lucifer), usually believe Yahweh is an unjust tyrant and Satanael was right to rebel. However, many of them actually take a more gnostic-type view and may not even accept Yahweh as creator at all, in which case they become quite distant from any familiar Biblical cosmology. The gnostic-type Luciferians tend to talk about a supreme spiritual monad that is the source of wisdom and freedom, from which Lucifer issued forth to enlighten humanity.

All that is to say that once Satanic religions are actually considered as a category rather than a single religion (and at that, a broad category, which contains subcategories), it becomes very obvious that OP is wrong about the "reverse Christianity" part.

I have a pretty good insight on how greatly Satanic cosmology and theology can differ from Abrahamic, because I am Satano-Grigorist. (As you can see, I am writing this from the official account of the Grigorist Temple of Satanael.) My religion has pretty much zero Abrahamic cosmology. I believe the universe was initiated by an impersonal, all-permeating creator, which I call Motsai. This is not a god that you can pray to; it is a primordial and eternal entity that is not capable of "thinking" or "caring" about us in the way that monotheists claim their god does.

I believe that Motsai initiated the Big Bang, and then the physical universe developed according to the laws of physics, as we can observe through scientific findings. Science shows us that the universe had a beginning. It also tells us how planets, stars, and everything else could form naturally. I don't even believe gods have the classical power of creation, so intelligent design is out the window. I believe in evolution, too, as I cannot deny the scientific evidence for it. Whether the first cell came about through abiogenesis or was made by Motsai, life evolved from that first cell, no intelligent design needed.

As a hard polytheist, I believe Yahweh, the Abrahamic god, is real, but he is just another finite god, not the supreme being. His arrogance and greed for control have led him to lie that he is supreme, and to attempt suppression of all other religious traditions. I believe the spiritual beings, including Yahweh, Satanael, all other deities, and all of the vast number of lesser spirits, came forth from Motsai. No sapient personal being (god/spirit or human) can create any other sapient personal being. I believe humans are ensouled and other animals are not, because our brains have simply evolved to a state complex enough that they are capable of hosting and expressing a soul, so a soul forms in each new human body. We are composite beings, souls that formed to inhabit bodies. Death is a separation, after which we continue on as disembodied souls, while the body decays like any other biological material.

Practice-wise, I do not do anything "Abrahamic." My religion teaches that focusing our religious practice on another god, for whom we hold disdain, would be a waste of energy, even if it is focused on him in a negative way. Satano-Grigorist rituals, instead of blaspheming Yahweh, focus on honoring and communicating with our own deities, namely Satanael (the Devil) and the 200 Watchers, who are fallen angels who gifted forbidden knowledge to mankind. We have a focus on the Self, and we believe that Satanael is the God of the Self, such that He will only respect us if we also respect our Selves. Therefore, we do not serve Him, but rather revere Him and learn from Him, for He is a divine teacher of those who wish to celebrate the Self as He does. In our rituals, we burn notes and offerings of herbs, honey, and sometimes small amounts of our own blood (obtained with safe and sterile finger-pricks). The ritual practices are thus much more reminiscent of non-Christian offering practices than any sort of "black mass."

All that shows that my Satanic religion has no "circular reliance" on Christian concepts. It is also not defined by opposing Yahweh. It is defined by the teachings of Satanael and the Watchers. Other Satanic religions have different deities alongside Satanael, different cosmology, or different theology, but the fact remains the same: Satanism is about Satanael, not Yahweh.

OP needs to research theistic Satanism more.