The relationship between the mother and her child is the number one priority here. So while this is a horror movie (mostly in the psychological area), it is also a Drama. And some of the best Horror movies (that are not Slashers or particularly explicitly violent) have been Dramas at heart too.
And while I get that the child may seem annoying to some and some decisions made feel rushed, the casting was good and the script was decent enough giving them all something to play with (no pun intended). The movie is very dark (both in tone and in visual flair) and while it does drift into expected (read cliché territory) and has somewhat of a downfall towards the end (and maybe for some a slow beginning), overall the positive things do win over ...
