The Babysitter is a fun, over-the-top horror/comedy, which will have very polarizing opinions, depending on the viewer.
I'm quite sure The Babysitter has some deep flaws. There are certainly some issues with the logic, probably anyway. Maybe the characters are a little one-note. The thing is, I was having way too much fun to care. 
From the comic-book text overlays to the major twists and turns to the child-engineering-prodigy trope to the humor-gore, I really, thoroughly enjoyed this movie. 
The tone started off as a comedy/coming-of-age story, but when it decided to delve into horror, it really delved into horror. It kept some of the comedic and coming-of-age elements, but from the first instance of horror on, it was without a doubt a horror movie, just a dang fun one.
I'd imagine this is a rather polarizing film. Either people will love some of the wackiness, or they'll feel it gets in the way of what The Babysitter could be. From some people, there will be eye-rolling and snickering, and from others, there will be belly laughs and big smiles. 
I highly recommend checking it out, but don't go in expecting a serious movie, or you'll be rather disappointed.