The now ending DC Extended Universe had several planned developments and paths, though a lot of these didn't come to pass. The haphazard changes to the shared movie universe were many times based around the reception of the movies themselves. 2023's The Flash is the most obvious example of delays and changes, with the movie coming out almost a decade after being announced. That movie was also once set to have a much different villain, and this could have changed the DCEU forever.
Source：https://www.cbr.com/dceu-abandoned-reverse-flash-plan-snyderverse/
