For a film based upon a highly popular horror video game, and for it to be released way after the actual time when its popularity was at its peak, it's surprising how much they missed the point when it came to explaining how Slenderman came to be as scary and as popular as it was in the first place.
The video game was super basic and never relied on too much to spook you. It was all about a fear of the dark and maybe some fears about ghosts as well. It was done in a first person perspective and whenever you see the Slenderman, your vision goes nuts, white noise to the extreme, and that's it.
In order for this film to follow suit, it simply needed to basically be The Blair Witch, found footage in dark woods for a majority of the film. Because in any Paranormal film about filming ghosts, what happens when they show up on footage? White noise and cameras malfunctioning. Found footage also never relies too heavily on story, relationships, or characters because it's usually stripped down to the basics to focus more heavily on fear tactics. This movie had random and irrelevant romances, and a mystery that is all over the place, and a lot of crap in plain daylight. It just doesn't work.... it's not scary, and it completely ignored what little story the games actually had, with collecting the pieces of paper notes in the woods.
In short, everything felt too unoriginal, unscary, overproduced, and overall incredibly stupid. It made sense that they made the movie, but zero sense in why it was made the way it was made.It missed the point entirely.