Marvel has unfurled their universe at a much more leisurely pace than DC.
Before the release of "the Avengers" in 2012 we'd already seen Iron Man 1+2, Incredible Hulk, Captain America, and Thor.
We didn't need any introductions on the fly. We knew who Loki was and why he was disgruntled.
DC is doing things the opposite way for some reason.
Keeping in mind that Nolan's Batman movies are a separate universe, we are only getting Man Of Steel, Batman v Superman, and then Wonder Woman.
Then we get the full Justice League movie.
Aquaman, Flash, Cyborg, and possibly Green Lantern will be thrown in without a proper intro.
Some of those characters are not well-known to the general public. You have to wonder what DC is thinking, they could be repeating the same mistake they made with "Suicide Squad."