it comes at night
It seems like one of the big reasons "It comes at night" is doing so horribly is because of the disconnect between the marketing and the movie they actually got. I'd argue something similar happened with Alien:Covenant. It's a pretty decent movie when it's trying to be something other than an alien sequel.
Yes, Cinemascore is amazing: It's a pretty objective look at what people who actually saw a movie thought of it. You can filter out internet writer "virtue signalling" spin as well as people pathetically using places like IMDB to vicariously make a political statement. It lets you strip out the bs.
That's not the same thing as a look at the film's quality.
Ironically your post provides a perfect test case.
Ghostbusters should have had less than a 20 on metacritic and BVS should be over 80.
...The Cinemascore for Ghostbusters was a "B+" not the F- your "20% on Metacritic suggests and BvS got a "B" not the "A-/A" your over 80 implies.
The bad legs of both of these films supports their cinemascore numbers.