It makes sense that in Fulci's subsequent meditation on his own warped mental state, A Cat in the Brain, he included scenes of his jaded self editing Sodoma's Ghost and ruminating on what the hell he is doing with his life. I was wondering the same thing while watching this movie.
No visual flair, no humour, no gore (well, not much for Fulci), no kills, no fun. The dubbed voice actors sound like they're reading off the script for the first time. Even the supposedly debauched bacchanalian nazi orgy that opens the film is boring.
I'm guessing even Fulci himself saw this as the nadir of his career. I can only surmise he was putting very little effort in at this point - nothing else explains the gap between the heights of his early work and depths of his later stuff.
Strictly for Fulci completists and even they will find it a little depressing!