You're screwing around. There is no evidence Miller's behavior was or is a chosen moral failing, ..
Haven't most of Miller's problems involved him being at a bar , and presumably drinking, which people would say shows your "true" self.
And if you want to write off what could be alcoholism, he still has a choice to go to these bars
There is no proof that there is some special mental illnes which absolves Miller of any responsibility in these matters.
Not everyone who sees Miller's problems is excusing Whedon's actual or alleged behavior. They just want to have Miller's criminal behavior acknowledged. (See below for more comments on that)
The fact so many other examples in film history did not need actors to be pals off-screen, yet deliver great performances / believable on-screen relationships means it was not necessary. You may like the idea of some of the MCU actors having some sort of friendship off-set, but that has no bearing on whether or not their performances worked. They were actors long before the MCU, and if any were known to deliver the believability goods in earlier perfomances, you can bet it was not dependent on their off-screen relationships to other performers.
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Sure, you can have believeable relationships on screen while not having it off screen.... but if you are doing an ongoing franschise, or heck, ANYTHING long term... MANY effective teams have a kinship way beyond just the job. For example, I have been involved with 2 different youth groups. The "effective" one the youth leaders bonded together in different ways outside of youth time. The 2nd one, where we all showed up to "do the job" but didn't truly care for each other past that time... we have lost youth in droves, even ones who were loyal during the pandemic.
Even another DC Film Universe group, Peacemaker, has shown such connecton, and many viewers connect with that, making it a popular series.
That kind of bonding will help generate support needed for things outside of the actual work. For example, how Scarlet Johannsan was able to get financial compensation for Marvel's poor release strategy.
With the DC Film Universe, fully 1/2 of the Justice League is basically out of it... Ben Affleck is dealing with his personal issues (which led to the Reeves one rather than an Affleck-directed one), Fisher has burned bridges so that the Cyborg solo movie will never happen (or basically happned within the 4 hour movie), and even after the Flash movie... will Miller be able to stay?
We're not quite sure what is going on with Cavill (who was well cast, but poorly written)... Momoa is busy with many projects, but i am sure is fine with being Aquaman independent of Justice League (though happy to do a Peacemaker cameo) , as is Gal Gadot.
And that part is a tragedy... Miller has been such a cheerleader for the DC Film Universe...and in fact, he said it himself atthe very start: "Multiverse!", where much later he was happy to be a part of Crisis (and actually pleasing fans of the TV version as well like myself).
Replace her with Cassidy Freeman!
Better yet -- Scarlett Johannson! (To me, they look like sisters!)