In 2013, Man of Steel releases. It's very much a self-contained movie in the vein of Batman Begins, with the only hint of anything more being a split-second WayneTech logo. It clearly wasn't trying to establish a larger universe
Three years later, BvS releases and retrofits Man of Steel as being the first act of a larger universe and story. In simple terms, it's as if the MCU went from Iron Man straight to Civil War. It feels like a movie trying to do three movies of build-up and sequel set-up in one. Practically stopping the plot in its tracks to tease stuff in very jarring, unnatural ways
The next movie is Suicide Squad, a movie that destroys any kind of consistent tone that seemed to exist between Man of Steel and BvS, and feels like an extraneous story that doesn't move a larger story forward in any way. None of these characters play a role in the subsequent movies.
Wonder Woman feels similarly extraneous, despite being a decent movie. It's a movie that feels like it's deliberately trying to separate itself from the universe's story to be able to do its own thing
Then Justice League plays it super safe, with a villain and threat that comes out of nowhere, cramming in characters and their stories that no one cares about, and trying to make a big event out of something that BvS already capitalized on. Like trying to make Avengers seem like a huge cinematic event after already doing a big team-up in Civil War
Aside from Iron Man 2, the early MCU movies never felt rushed. They all took their time to establish their heroes, yet all felt subtly connected in terms of world-building and tone. Every movie added a little bit more to the larger universe. Then when Avengers came around, the heavy lifting was done - heroes, villain, and threat all established - so the movie could focus on the chemistry between the team and building up to the team coming together for the first time.
By contrast, the DCEU started with a movie that existed almost completely in a vacuum, and then rushed to a Avengers-style event film with their biggest characters, then did movies that felt disconnected from those movies, then tried to another event film despite already taking the wind out of their own sails
Those are just the issues tonally, narratively, and in terms of building a universe. Nevermind the individual issues with the movies themselves