JL is a tough nut to crack. when I think of JL, I think of the cartoon version... the one where they live in the "Watchtower" and each character is (already) the best version of themselves -- which means -- there's not a whole lot of room for character growth if this were adapted straight to a motion picture version of the same thing, because these characters are presented to us in this cartoon as 'already developed' in the show's ongoing status quo.
I think Snyder chose to set this "version" of JL, as the "end-point" of ALL his planned story arcs for these characters in his Snyderverse... this "ideal" version of JL, was to be the "target" for what his characters would grow INTO, by the time he was done with them. so with that in mind, he sort of rewound the clock on each of these characters, and placed them each in a dark place, to start off with.. why? so they would have room to grow INTO that ideal version.
so when we first meet Batman in the Snyderverse (for example), Batman is a dark, cynical, jaded 'ex-hero' who has lost his robin and he's arguably at the darkest point of his life when the Snyderverse begins; Aquaman is exiled from atlantis and shunned by humanity and he's arguably at the darkest point in his life too; Cyborg is a tortured soul who hates what he's become, and he's arguably at the darkest point in his life; Wonder Woman has "turned her back on humanity" and is exiled from her homeland, and all alone in the world, and is arguably, at the darkest point in her life; Superman has no faith in humanity anymore, (he broke his "do not kill" rule in the VERY first Snyder film -- this is NOT your grandpa's Superman), he has come to wonder "why bother?" in Lois Lane's bathtub and he's, arguably, at the darkest point in his life... and etc, etc...
^^ I mean, holy crap! talk about a depressing bunch of characters! these are supposed to be "superhero movies" and everybody's walking around like manic depressives at the end of the(ir) world(s).
^^ presumably, under Snyder's watch, each of these characters would go on a journey of self-discovery which would see then 'grow' INTO those ideal versions of themselves, whom we all know and love, who live on the watchtower solving crimes on saturday morning cartoons....
....but his "starting point" for this journey was SOOO dark and depressing, for each of these characters, that the audience (and the studio) lost interestr and BAILED before he even got started. nobody could embrace these dark jaded versions of these characters.
after all, a "normal" character arc doesn't see this kind of "darkness" until act TWO. something along the lines of "...boy meets girl, boy loses girl, boy gets girl back in the end" (that KIND of thing).
we normally get to know (and get to LIKE) a character first... THEN the writer throws that character into the darkest point in their lives... THEN the character overcomes their conflict, and comes out the other side changed for the better. (aka: a proper arc)
but Snyder chose to start his epic character arcs in the middle of "act TWO" for EACH of these characters.... (presumably there's a backstory for why Batman is so jaded and bitter (as evidenced by his effigy to Robin) but Snyder thought the 'act one' part was unimportant. he wanted to START the story with batman already AT his "darkest-of-days", and go from there ...and THAT dark depressing "starting point" made EACH of his characters inaccessible.
we couldn't sympathize with a superman who KILLS his adversaries on his very first mission; we couldn't sympathize with a batman who WANTS to kill superman in return; we couldn't sympathize with a wonder woman who has "turned her back on humanity"(etc). these are NOT the ideal versions of ANY of these characters LOL.... because Snyder insisted on starting each arc in their respective act TWO, "the darkest-of-days", for EACH of the JL characters.
a better strategy would have been, to present each of these characters in their own "hopeful" first-episode-movie (like WW1), and THEN throw them all into darkness for act two -- to show Batman at his 'best' before robin died (to gain the audience's sympathy for Snyder's version of the character), BEFORE we see him presented to us as a jaded murderous ******* (with whom the audience cannot sympathize, even if they TRY).
in the case of WW, Jenkins went back to her Origin and told the story of her coming into the world, full of "superhero ideals" and full of faith in humanity.. so Jenkins got the opportunity to go back BEFORE the Snyder version, to a time BEFORE Diana "turned her back on humanity".. to a time when the character was actually someone whom the audience could actually identify/agree with.. and this is why WW1 did so well at the BO (when compared to all the "dark" and cynical Snyder-characters populating the rest of the DCEU).
in that sense, WW84 should have brought us to the "act two" of Diana's arc, where Diana "turns her back on humanity", and grows more towards the cynical jaded ex-hero that we see in BvS. but it seems like Jenkins has decided to buck against Snyder's "version" of the character. so now it's almost like we're dealing with two different "versions" of wonder woman in the DCEU -- the Jenkins version is not quite lining up with the BvS movie.

LOL
the only way this works now is if WW3 is yet another prequel which takes place before BvS -- if they use the WW3 movie to bring Diana to that point where she "turns her back on humanity" (to line up with the Snyder version).
but that would suck for Jenkin's "trilogy" (as a whole) because that would mean she basically has to END her trilogy on the proverbial "Act TWO" of Diana's character arc (as discussed above). Jenkins would need to END her trilogy, at Diana's "darkest of days", just to line up with Snyder's "starting point" that he used back in BvS. (and I don't think Jenkins will be keen to play ball on that field -- she will want to wrap her trilogy up with a neat bow, where Diana comes out the other side 'changed for the better. aka: a proper arc' -- I don't think she will be keen to END her trilogy with Diana "turning her back on humanity")

(they really should have done that in WW84, and then set WW3 to take place AFTER the JL movie).