Horror movie sequels are hard to make. Do you rehash the original or do a new thing? Bring back the old characters or start with new people? Continue the story or just do whatever?
I have no idea what this Insidious: The Last Key did. I never saw the other (three?) movies, so I can't say. But I can say that this one is B-grade horror at its best.
An old lady who can see ghosts gets a job to go back to her old home so she can confront some ghosts of her own. See what we, the movie and I, did there? Because her dad was abusive so she has trauma and that can be seen as metaphorical ghosts and there's real ghosts. It's supes cogent.
The jump scares are few, the jokes are peppered, and nothing really does great. Like, no great was had. Some fine happened. Some okay squeaked in there. They got me on one twist, double downed and kinda wasted it. Then threw in another and I stopped caring.
In this movie, humans are the real monsters. Except when a demon is tricking or manipulating them? The whole thing is just a mess that plods along. I wish I could say it is at least fun, but I checked my phone during this one which is a sin in my world that gets you banned to hell where you watch this movie.
Still, if you can't find anything on streaming one hungover day, yeah, there's better movies.