I also hope they focus first and foremost about getting the individual characters, their journey's, their supporting casts, and their own environments first ,before getting hung up on trying to make them all fit together in an overarching storyline.
At the end of the day, if the goal is to have a strong shared universe, that means having strong individual characters, and strong individual films as a foundation.
Get the GA, not just fandom, interested in these iterations of Clark Kent, Hal Jordon, etc first, so that people will eventually look forward to seeing how they interact down the line.
There's really no rush to start team ups and overarching threats .