What the fuck is wrong with DCEU
The inconsistent and volatile quality of the writing will be a start, flaws in characterizations, tries too much to be like the MCU.
If they wanted the DCEU to be successful they should have taken exemple on the DCAU to begin with, which was very successful due to its realistic and often dark stories but also lots of hopeful and inspiring moments, they knew how to place humor without it being a detriment to the story and tone of their series, focus on characterization and real-life problems, consistent continuity and ties between the series, etc...
Of course the DCAU wasn't flawless but it's the best example of why DC has consistently been and continues to be better than Marvel in the animation department.