"Zack Snyder's Justice League" is a 3 out of 5 stars. Keep reading...
There really isn't anything Earth shattering or groundbreaking about this movie. But what it does is ties "Man of Steel" and "Dawn of Justice: Batman vs Superman" together. I have to stress before you see this movie rewatch the first two. It makes more sense and flows better.
Not horrible but not amazing. Worth watching at 4 hours...and also "Dawn of Justice" is 3 hours long. Just FYI.
I will say this...a few extras I didn't expect popped up. I won't spoil, but again the few pop ups weren't enough to warrant a new movie BUT I think they did this movie to more align it with the DCEU (DC Extended Universe) as they are looking to compete with the MCU (Marvel Cinematic Universe) to make the films more chronological and fit together.