Whoops, I didn't even read that part earlier, thanks for clarifying. Not sure how much that changes my post overall, maybe a little but not worth going back and editing.
I don't know that Snyder's Justice League would need to be 3.6 hours long if Warner Bros. also let him finish his planned 5 film arc. That's a whole other can of worms to discuss, but should probably be mentioned at least, because WB scrapping those plans led to re-writes and new plans for Justice League, both when Zack was planning/filming it and when Whedon took over.
As much as I enjoy and appreciate BvS (and always will, particular the UE), this is really the single biggest driver of JL being DOA. BvS remains the only movie to not break $1 billion after scoring more than $150 million ($166) in its opening DOM weekend. Keep in mind that movie made something ridiculous like $450 million worldwide on its opening weekend, basically half of its entire BO run in its first three days.