It was enjoyable, but it suffers from a lot of things.

Rating: 6/10 (27 November 2017)

Lets get the general spoiler-free ideas out of the way.
The movie suffered the most from sudden change in direction the studio is taking for the whole DC movie verse as it shows in this movie a lot. We all know how they aimed to build the whole thing towards Darkseid, with the whole JL part 1 and 2. And they were done most of the part when they realized (test screening) that it won't work. I mean everybody said it from the get go that they are rushing to bring a similar ensemble movie as Marvel is with Thanos. The only difference being, how Marvel built up to this point over several movies.
Now we have sudden tone change, that shows in the colors,the dialog and generally having more comedy in the movie overall. And I'm most certain Joss Whedon takes credit for that. We are familiar with Snyders take on these movies, and we already seen what Whedon brought to the Avenegers. They are like the two sides of the same coin, and cannot mistake them from one another. Here you could see which scene was added by Joss.
The problem is that such a sudden change with a movie that was being built up to being something else entirely kind of undermines not only this movie, but the ones that came before.
This movie is happening just days, a month at best, after BvS. Batman killing baddies, being dark and overly brooding, hell his hate towards Superman suddenly does a 180. Like it never happened.
Since the stakes are being brought down (just so they can turn it up again at one point) the sudden introduction of Doomsday, and the death of Superman becomes an even more wasted opportunity.
GOING INTO SPOILERY TERRITORY!!! The movie does mostly a great job at ripping the characters out of the comics and bringing them to life on the big screen.
I am saying mostly since 2 characters suffered, and suffered hard they have.
Steppenwolf is wasted baddie for this movie. He doesn't work visually, as he looks like a huge CGI mess, and he doesn't work as a villain in the overarching story, as his presence is made minuscule in minutes. And that's kind of sad, provided he is considered a god, therefore one would assume the stakes are high. No they are not.
I mean after the lackluster revival of Superman he pretty much single handed beats Steppenwolf to a crisp in 2 minutes.
We are 5 movies into the shared DC universe and we already defined Superman as this guy who can be resurrected to beat up gods(Steppenwolf states that he single handed hunted down and killed the old gods, which indirectly means Sups can do the same, and easily for that matter). So what can the future hold in store for the DC movie verse if we have this hero who can shrug off death and beat down gods? The second character to suffer was Flash. When it comes down to DC I'm a Flash guy. I think he embodies selflessness and hope-fullness better them most other founding members of the JL. Its due to his strong sense of justice, sourcing from his mothers death and false incarceration of his father, he pushes trough his obstacles in a way we can relate to him better then Superman or Batman, who both seem larger then life.
Besides his father being imprisoned there was nothing Barry Allen about this Flash. He was more of a poor mans Wally West. So if you hope to see your favorite speedster in the movie, you might come out of the theater with a bitter taste in the end. Especially seeing how the rest of the cast was done justice.
The story was kept simple, so there really is nothing I can add to it. We have all seen this kind of ensemble movie be done several times. In truth I wasn't expect-in much of it to begin with, but I'd like to see Snyders cut of the movie, just for comparison.
They had several opportunities to make this particular story slightly more interesting, but they just wouldn't leave that comfort zone.
At one point it felt like Cyborg was the 3rd Motherbox, which would have made a more interesting movie.
Would have loved to see the Female Furies. They are Darksides elite force, so they would have worked just as well for a build up movie. Would have worked better for an ensemble movie to, by showing each individual member of the JL fighting. And since they aren't as strong as a New God, the stakes would have been kept higher for future movies.
Aquaman was in the movie, so why put the location of the final fight as far away from water as possible. Give him a glass of water, make him spit on and flip of a Parademon. Just include some water based liquid into his scenes. He was mostly in the background, which is shame, as he was quite enjoyable whenever we got the chance to see him interact with the others or in action.
It was the culmination of the small misses here and there that overall brought down my rating, but in no means does that mean it is not an enjoyable movie. It had done steps in the right direction, but I will not speak of them until I'm certain they were intended and not done by mistake.