More than some other reviews I've read, The EW review seems to get to the point of why the film doesn't appear to work (I haven't seen it yet):
http://ew.com/movies/2017/11/15/just...alflow_twitter
Frankly, it seems like JL has the worst parts of Thor: The Dark World (the villain), The Incredible Hulk (the CGI), and Suicide Squad (inconsistent tone, scenes that feel out of place). Fortunately it seems to be buoyed by the cast who are seemingly being universally praised as having good chemistry.It’s obvious to anyone watching Justice League next to the other DC films that the studio brass handed down a mandate to lighten the mood and make things funnier and more Marvel-y. And, to an extent, Justice League accomplishes that. But it also feels like so much attention was paid to the smaller, fizzier character moments that the bigger picture of the film’s overarching plot was a second or third priority. Some day, hopefully soon, DC will get the recipe right again and duplicate Wonder Woman’s storytelling magic. But today isn’t that day, and Justice League unfortunately isn’t that film. C+
A final RT score in the 50s or 60s wouldn't surprise me. Average rating will probably end up around a 6.5 out of 10.