There’s a lot of characters and backstory in Forever Evil. I agree that it would be better as a series; if it were to bear any resemblance to the source material.
In the same way that The Flash was reduced in scope and characters from Flashpoint; FE would have to be reduced as well. But how? Geoff Johns could do it. Would there be an Earth 3? It’s not been a concept in the DCEU. They removed Reverse-Flash from Flashpoint; so I assume that Pandora, Atomica, The Outsider, Johnny Quick would be out as well; replaced by more familiar characters.
And Forever Evil was a singular cross-title event; but it was just a small part of the New-52 Justice League storyline that concluded in Darkseid War.
So complicated, so how would it be simplified to a film?