Was The Snowman really that bad?

Yes, it was.

Being facetious aside, why was it that bad?

Released in 2017, The Snowman had so much promise. Based on a popular Jo Nesbo novel, the director of Let The Right One In Tomas Alfredson and Michael Fassbender involved, and Martin Scorsese executive producing (not to mention his regular editor Thelma Schoonmaker working on it). So what went wrong?