I don't know the Nightmare on Elm Street series, but I don't think the Saw films have jumped into humour. It's true that the Jigsaw character has become a bit less enigmatic, but I prefer that. Perhaps I should say that I prefer SF to horror generally. The Saw films are more psychological thrillers than horror films, and it's appropriate to delve into Jigsaw's philosophy and motivations, and now his legacy.
That said, part of what I liked about the 4th film was gruesome, macabre machinery is back, because in the 3rd film that side felt a bit unimaginative.