Was the movie good? Yes, but it needs some improvement; it could be better. I've enjoyed the movie, for the most part. However, there are scenes that I found stupid and had lack of purpose. To be honest, I think the directors, producers, screenwriters, etc.. had a good idea on how they wanted the movie, but this wasn't it. Don't get me wrong, the suspension and/or tension was not bad, but didn't impress me or some of the audience. In my opinion, this had the potential to be one of the greatest movies of 2020. Yet, it fell face flat towards concrete. Especially the last half of the movie where they are just dreaming of Slender Man, seeing his shadow, and do not get me started in the whole hospital scene. What they could have done to make the movie better was to use the plot structure and follow it thoroughly. When it comes to the plot structure, it lacked rising action, climax, falling action, and resolution. All that was told was that Slender Man was "real" (in the movie, not in real life) and then was being attacked or targeted. That covers exposition and conflict. This is my perspective, maybe someone disagrees with me. Even if there were a full plot structured movie, it still needs a fix in the tone, setting, perspectives, details, etc.. It had poor dialogue and unreasonable "jump scares" if you want to call it that. The so called jump scares could have been improved so much and brought up so much tension and suspense that would make you fear of what is going to happen next; JUST HOW I LIKE IT. Lastly, the ending was not great at all. Just overall, it was a poor, not amazingly great movie. It can be somewhat fun to watch it with friends. But, I wouldn't really recommend this movie.
I give my advice on how to improve the movie just in case they decide to make a sequel.
Now, I don't really think it was the best idea to make this movie. There were real murder cases where children have murdered people for protection against Slender Man which have sent them to either jail (5% of the time) or to a mental institution. Like as we all know, Payton was a victim of 19 stabbing wounds caused by Megan and Annis thinking that if they killed someone, Slender Man would not come after there family. Another case of a 14-year old female who turned her house on fire due to this as well. And yes, I did my research. The victims family and the family of those children who caused harm in these beliefs, strongly discouraged and didn't approve this movie. It's like an open door on more fears, murders, deaths, victims, etc.. Even though this movie was not directly based on the real life events caused by Slender Man, it was based on the fictional, urban legend, character which triggered allot of dark and dangerous events.