Ever since Zack Snyder's modernized take on Superman in Man of Steel, a movie where Pa Kent was concerned about how the world would react to the existence of a super powered alien and Superman was eventually forced to snap Zod's neck, the discussion surrounding the DC Extended Universe has always had a specific focus on tone. Batman v Superman: Dawn of Justice also saw a polarized response from fans and critics because it leaned into that darker tone, Suicide Squad apparently drastically changed tone through reshoots and post production due to the reaction to Batman v Superman's tone, Justice League was promised to be a lighter tone, and Wonder Woman was praised for the way it struck a serious-yet-uplifting tone.
As such, it should be no surprise that tone is once again the word of the day when it comes to Justice League's reshoots. "Reshoots" is always such a loaded term, and the aforementioned changes to Suicide Squad only compound that fact with Justice League, with rumors of truly massive changes taking off even more once Joss Whedon stepped in to complete the movie after Zack Snyder's family tragedy.
In a recent interview with Joe Morton, the actor that plays Silas Stone, the father of Victor Stone, AKA Cyborg, Morton was asked about his experience with the Whedon -led reshoots, to which he said the tone of Cyborg - and possibly the movie as a whole - was being altered from the work that had already been completed by Snyder. Needless to say, this quote kick-started the speculation around the internet into high gear once again regarding just what kind of movie we'll be getting in November. Was Joss Whedon brought in to alter the movie's tone after all?
In the simplest and most concise of terms: No. Joss Whedon took over directorial duties from Zack Snyder because the latter needed to step away for personal reasons. This was not an orchestration by Warner Bros. to get more tonal control over the movie and the reason for choosing Whedon has nothing to do with tone either. Even so, while the purpose of bringing Whedon on may not have been to change the tone of the movie, that doesn't mean the reshoots won't have that effect to some extent.