If this movie had had the balls to just be an outright comedy, I think it might have had a chance of really working. But by trying to cling to some kind of "real" horror story and attempting to mine real scares and genuinely disturbing moments from the material, it really loses its way.
By not firmly picking a lane between comedy and horror, the comedic moments in Exeter (which could have had promise) don't ever get a chance to really take off and the moments of dramatic life-and-death struggle just seem ridiculous. Rather than working together and potentially complimenting each other, the horror elements in EXETER only seem to undermine the comedy and the comedy makes the attempts at a serious horror story seem silly and ridiculous.
Some movies to a great job at balancing real laughs with real scares, but they seem to ultimately have a firm grasp on their tone and what kind of movie they're trying to be (a horror movie with comic relief vs. a comedy with some occasional horror and scares). Recent movies like HOUSEBOUND or BLOOD PUNCH are great examples of movies that pull off this tricky balancing act by establishing a tone and sticking to it, knowing exactly what kind of movies they are trying to be.
EXETER, unfortunately, never seems to quite find a tone that works for it. The result is a well- meaning but muddled movie that aspires to be both a horror and a comedy but ends up missing both targets completely.