I agree with many others that the ending doesn’t entirely work. An unspoken rule of storytelling is that your midway twist is also not an ending, which this film purposely breaks.
But also, as a film about burning your clientele alive, I found it more than mildly thrilling. And as the film would be eager to point out, that of course implicates me. Which is smart. If you like the film, you are what it rails against.
Either that or you’re a perfectionist with highly demanding clients. Hard to tell.