The killer's voice... (Spoilers)
I understand that unlike 2017's 'Jigsaw', they wanted to make it clear from the start that it was a copycat and not the original Jigsaw who was responsible for the murders, but the altered voice they chose for the recordings sounded strange.
Not strange in a sinister or menacing way, but more akin to a slightly pitch-shifted voice of some random non-binary Youtuber or transgender TikTok'er, just that sort of condescending holier than thou tone, devoid of any charisma.
Not to say that all gender nonconforming individuals possess these negative qualities, but a lot that I've encountered have been seemingly very full of themselves and opinionated, yet their voices were dull, insecure sounding, and lacking confidence.
The voice they chose was too far removed from the template established in the previous movies. It didn't necessarily even have to be deep and gravelly. A sneering, nasal tone along the lines of Anthony Hopkins in the Hannibal Lecter films could have worked.