As a movie, this sort-a worked out OK. Lots of big action sequences, a team of heroes and heroines, some comedic moments though not much emotion. The “good” guys spent all but an instant wrestling with the morality of resurrection hingeing on the old adage of “the greater good” for example.
Yet as a film, you have to wonder why two of the tribes (Atlanteans and Amazonians) went to extraordinary lengths to “seal” the unity/mother boxes in temples/tombs when the Steppenwolf just teleported into them, and then teleported out again. All seemed a little pointless other than to show off some set design and set pieces. And the box of Man was just buried so nobody could ever find it, yet somebody did (which was not explained) and, even if they hadn’t, these boxes send out a homing signal when they wake up so Steppenwolf would know where they are. Odd that.
We’ve seen the Green Lanterns in other incarnations, so it might have been more prudent to spread the stones far and wide and take a bit longer getting to the big endgame (assimilate earth) than rush to it in a fraction of the time that Marvel did getting to Avengers: Infinity War. Though, if they had restricted it that way there is a lot of similarity between the ideas (megalomaniac seeks multiple power stones/crystals to ensure destruction).
Justice League felt like a collection of pieces that didn’t add up to more than the sum of its parts. It was still a visually good movie, and worth the runtime, but there wasn’t the payoff we have come to expect with the Marvel canon.