Presumably, it depends on whether or not you think possession is a real thing in the real world or not. I could see it being way scarier if you see it as something that could happen to you or someone you know and care about, or it could just come across as being really goofy if you don't think it's a real thing.
It probably also helps if you're capable of feeling bad for the girl as a victim or her mother having to deal with the horror of this terrible thing happening to her child (which might even be more powerful if you yourself are a parent and are being confronted by the idea of a parent being helpless to protect their own child).
FrozenBananas posted...
Even the famous The Exorcist (1973) is pretty boring to be honest, and relies too much on the make up and special effects for shock value
It's one of those "It was scarier at the time" sort of movies, just because audiences at the time had never really seen anything like it.
Modern audiences are way more jaded, way more experienced with this style of film ( https://tvtropes.org/pmwiki/pmwiki.php/Main/OnceOriginalNowCommon ), way more atheist, way less likely to give a crap about the little girl or her mom's suffering because empathy is rapidly becoming a lost art. And older suspense-driven movies in general don't work as well today because people's attention spans are so much shorter than they used to be.