I suspect that Crowley was undiagnosed autistic. In addition to that battle, his upbringing, which was repressive even by Victorian standards, would have messed anyone up. The man carried those dysfunctions with him for the rest of his life.
I am not overly concerned about any adult followers that he "abused". They had Will just as much as he did and were perfectly free to walk away, as many did. He never held anyone against their Will. In their weakness, they may have held themselves against their Will but that's on them. However, my rage with Crowley is that he did have direct experience enough to question his social programming concerning animals and he knew that religious attitudes towards sacrifice were subjective methods and that there was no inherent power in the act. Still, according to Symonds, he murdered at least one cat in horrific circumstances (probably two - he wrote in a way that belied no shame about such acts either). Animal sentience was disregarded by most at that time but he'd read Nietzsche, there were successful British campaigns at ending vivisection during Victoria's reign and personal deprogramming is a central tenet of Thelema. He had no excuse. He behaved as a squalid, drug-addled degenerate would.
As a writer, nothing could ever exceed his opinion of himself so there is no space left to praise. He was a decent writer though that wasn't unusual for someone of his education. The passage in the Confessions where he reads a mediocre poem to Yates and describes Yates as envious afterwards, is clearly delusional. His dependency on alliteration becomes rapidly annoying and, in his magical writing, his retaining the G.'.D.'. Qabala reveals a surprising reluctance to revolt.
None of this changes his world changing conclusions on magic. 666 took a jumble of medieval superstitions, opaque references in classical literature, Nietzsche, interminable Eastern ponderings, French poets, Victorian Egyptology, sifted through much of the chaff and streamlined a vision of the heroic individual in the midst of a life-affirming universe. In those fragments he saw a way to transform the individual soul into a god. It is perhaps fitting that the man who did that was, more than most, in need of the transformation of his own soul.
Degenerate? Yes. A genius? At times, also yes.