Tag is a difficult movie to rate. The soundtrack is beautiful, the CGI is...shall we say, it could use improvement? The acting to me is good, but I can see if some consider it "over the top".
It's a very Japanese movie with Japanese humour, so many Western people might not understand it or frown upon it.
It's also a very "Sono" movie. Sion Sono (I think as far as I remember, he comes from the pinka aiga genre and his wife is a former JAV star) made many movies about patriarchy and the whole "men vs women" thing. Love Exposure, Cold Fish, Guilty of Romance...all with pretty despicable male characters and often with the empowerment of women.
Tag makes it clear early on that it's a very female movie. Up until the final part, there isn't a single male character (if we don't count a literal "pig") in the film. Then, as we cross into the "real" world, we see nothing but male characters (and not in a flattering light).
I see Tag as a metaphor. Men control women, they oversexualize them (if you watch closely, all the school girls seem to be clearly older than regular school girls) and show them as objects. So we can see the final scene as a freeing of male shackles, aimed at (Japanese) women?