I dont get all the hate towards this movie. I would understand if the general consensus was it was a "meh" movie because to me at least it was. Not good but not bad just.... meh. Its definitely a fun movie to watch since its pretty fast paced compared to the other movies in The Conjuring franchise which usually have a slow-ish burn to them and start off with minor things and inch into the heavy jump scare type content whereas The Nun has a lot of jumpscares all the way throughout, some of which are cheap and uninspired, but there are also plenty of solid scares that you will not be expecting.
The story could have been better but its nowhere near the worst I have ever seen, and I quite liked the ending how they brought it all home in a way. Another problem I had was with Valak. In the previous movies where she is seen you usually get an eerie gut feeling and mysterious vibe from her but in this movie shes just in her true demonic form as seen at the end of The Conjuring 2 but instead throughout most of the movie which I think takes away some of the originality from the character.
Those are really the only negative things I can think to say about it right now. Other than that I quite enjoyed everything else about the movie: The actors were great, I LOVED the atmosphere and visuals, new take on demonic hauntings with some being actual physical beings (this may be a negative for some because it takes away from the "realism" of it but I thought it was cool), the ending was neat, sound design was pretty solid, had a gritty tone to it unlike other movies in the franchise, some good scares here and there. I'd say if youre a fan of the series definitely give this a watch but dont watch it like you would the other movies, go into it not as a Conjuring film but as its own thing. Kinda hard to explain but basically I enjoyed it for what it was and think its an okay entry in the franchise. As I said at the beginning: not great but not awful either. Give it a chance.