WW may need a little more exposition but will she need any more individual time than say Storm in the first X-Men movie?
God, I hope so, since Storm was completely wasted in X-Men
Who else will be in this movie? Flash? Martin Manhunter? Green Lantern or Arrow? They can probably be summed up fairly quickly by either flashback or narrative.
I think the best way to sum up a hero is by what they do. Show them in action. Show them saving innocents, show what powers they use to do it, show their attitude and personality as they do it, show what roles they play within the team. Then follow them back to HQ and show their personalities in more depth through their interplay.
As for origins, I consider those optional. Every character has a past that shapes their actions, but not every story that introduces a new character has to explain where that character came from. We didn't get an "origin story" for Indiana Jones until the third movie and the spinoff TV series. We didn't get an origin story for James Bond until 44 years into the film franchise. Where a character came from is only important inasmuch as it informs their behavior and values now. You could show that in dialogue without flashbacks. Have Clark and J'onn have a conversation about being the last of their respective species and what it feels like to be aliens on Earth, with the differences in their perspectives coming from the differences in their histories, with Clark growing up among humans and J'onn coming to Earth as an adult. Have Barry give Hal a chewing out about how his arrogant attitude and space-cop perspective blind him to the concerns of the street-level civilians that Barry, as a crime-lab tech, has to face on a regular basis, and maybe throw in some Aladdin jokes about his magic lantern and ring. Have Diana comment on how much simpler things were back on Themyscira, growing up with the Amazons. Maybe have Hal and Bruce comment on their mutual skepticism about Diana's claims of being a product of Greek gods and myths. That way, you're revealing backstory at the same time you're doing the more important job of revealing character.