Cavill’s future as Superman has been confusing since the release of Joss Whedon’s was in development, he had seemingly left the DCEU, so he wasn’t going to be part of even if the story had a place for him.

Source: https://screenrant.com/why-supergirl-is-a-prisoner-in-the-flash-movie/

Shortly after Carpenter's statement, Michelle Trachtenberg (Dawn Summers) opened up about Whedon’s inappropriate behavior and how he was not allowed in a room alone with her.

Source: https://www.buzzfeed.com/claudiasantos/toxic-tv-sets