I'm not sure why people are disappointed with this movie.
[SPOILERS WARNING.]
The movie isn't even related with the games' lore. And the fact is that it was announced before the movie was out. Needed to say this since people got confused when they made Vanny William's daughter. She is Elizabeth in this movie.
Sure, we thought that the movie would be more horror, but Five Nights At Freddy's always first attention is the story and then the horror to try and scare you. Plus, even in the game I'm sure we hadn't saw some gore than we're seeing in the VHS tapes on yt.
Most people are disappointed because when the animatronics built a pillow fortress for Abby. But that scene shows that the children in the animatronics are and will be kids who want to play sometimes. They will never be just kill machines. Thought, a theory could be that they just wanted to manipulate Abby to gain her trust and to be easier for them to put her in the springlocks.
The last, is the springlock failure scene. People are disappointed about it because William didn't scream or there hadn't shown so much blood. And the iconic "I always come back." line was said too fast.
But, the springlock failure scene was actually realistically correct. Because the springlocks literally 'stabbed' William's lungs, so he couldn't scream. Plus, as the creator of the springlocks he knew he needed to maintain calm, if he didn't then he would activate other springlocks and make things worse. So, the reason he said "I always come back." fast was actually his last breath.
Me personally this movie is very good to watch. We have things we expected and wanted to see in the movie, ex the missing kids and the springlock failure, we have popular youtubers in it, like Matpat and Cory. The popular character William Afton, and the security guard everyone played as in Fnaf 1, Mike Schmidt.