Well... it's better than Justice League War-- but I have a hard time saying it's good.
And I think I figured out why! It's trying to be both a Justice League movie and an Aquaman movie at once. And while I can see no problem with adding a story within a story, as is with from what I seen at least it's probably not a good idea to do both.
Superman surely matured... for a moment, as did Wonder Woman... for a moment, Batman was certainly more tolerable, but perhaps the best character in the movie was Aquaman himself. But again, I felt it would be more appropriate to make an Aquaman movie instead.