The DC Extended Universe wasn't even really a thing when Man of Steel was released in 2013, and whereas Iron Man was always supposed to launch a shared world for Marvel Studios, Superman's origin story being a launching platform for something bigger was never really in the cards.
In fact, it wasn't until Comic-Con a couple of years later when Batman v Superman was announced that the "DCEU" started taking shape, and it's since been something of a rough ride for Warner Bros. While the Marvel Cinematic Universe spawns hit after hit, the response to many of the DC Comics adaptations has been mixed, with questionable creative decisions and a number of big mistakes.
That may actually be an understatement for some of these, because not only are they big mistakes...they're downright unforgivable! They should never have been allowed to happen, and had they not, the DCEU would probably be in a much better position than it is today.
Sure, things are slowly starting to look up for this shared world, but undoing the damage caused by these blunders is no easy feat, and the ramifications are likely to continue being felt for years to come. Whatever mistakes potentially come next, however, surely can't be as bad as these...