We don't have any information to confirm that Superman will not have significant interaction with the team or will not be integral to its founding.
The group looks pretty well founded already if you ask me, and that's without Superman being there as well.
And with everything that's going on in this film, it's only logical to assume that Superman won't have much time to even get involved with this group until the final battle...much less be integral to its founding, especially if the means to his return takes up a lot of time to take place.
The only way that Superman would have a chance to having a good amount of screen devoted to interacting with the group would be if he was revived around the same time that Jack Sparrow was for "World's End" and if this film was as LONG as "World's End".
Please. His absence proves his importance. If he was around, it would be too easy. If he was around, the world and heroes wouldn't be galvanized by his sacrifice and example. Characters of great power and significance to teams and to narratives can be removed for effect, as Gandalf was for LotR.
If anything, the very concept of the DCEU's JL is already insulting to its members as well. Bruce and Diana form the group because Superman is no longer around so what does that say of the entire group then? That it takes 5 costumed heroes to make up for one?
The threat that Darkseid's minions brings should have been so great that even with Superman, it wouldn't look like the group would have a solid chance of surviving the onslaught.
I would have had Bruce/Clark come to an uneasy truce after intense conflict in BvS. They're not quite BFF's, but they've somehow earned each others' respect. I'd have the two of them seek out the rest of the JL. That way we'd get to see them interact and have character development for both of them and shortly after, the rest of the JL.
And had the executives for Warner Bros seen this post, they would have saved millions of dollars from having to hire Snyder to come up with a story with JL when MrsKent's post pretty much nails on what would most likely have been a better story arc for this film.
I honestly don't know why Snyder believes that by having Superman involved in the recruitment, that it would make things too easy. Just because he's Superman, it doesn't mean that everyone would be willing to follow him right away. BvS showed that the world was divided when it came to Superman's presence/actions, so it would be reasonable to assume that members of the JL would feel the same as well.