Honestly, the movie was way too long and drawn out. If the original Justice League movie never existed and this was the first movie to be released, it would be sub par at best. Most of the reviews are comparing it to the awful version we got to see in theaters so of course, this version is receiving high praise.
On my opinion, the movie is average and the storytelling is not that impressive. Compared to any of the MCU movies, this movie is nowhere near as good. But given the DCU movie track record, is this probably the 3rd best movie behind Man of Steel and Wonder Woman.