Maybe it is not just that McGrath in the lead is that bad. I think it is possible she was just directed that way, because the leads who play her husband and gay best friend have the same exact issue. None of them ever reacts to the violence that happens to them and those close to them. It's actually rather surreal. After awhile, a total lack of their ever having a connection to what has happened before, tends to make you not care at all about what happens to them next.
And killings based on the 7 deadly sins?? Yeah, that hasn't been done before.
It is really a shame, because this series actually had some chilling plot twists and turns and does have some well-shot scenes that made it worth sitting through. Some of the supporting cast is terrific, but there are just way too many unbelievable moments, totally lacking in any emotion.
"Scream Queens" and, to a lesser extent "Scream," tried to be too clever about their villains and it frankly got really tedious, really quick. I am still amazed that I put up with "Scream Queens," in retrospect. The self-parody of that series was headache-inducing.
"Slasher" sticks with some effective horror and gore, and even has an entertainingly creative last moment. I do think a flaw in the costume design (eye holes a little too big) made it easier to identify the executioner, but at least the killer's identity wasn't convoluted.
If they only had lead characters that actually were able to relate to events that were happening to them, at least as much as some of the supporting cast, maybe we'd care a little more.