For many reasons the DCEU/World Of DC (if you prefer) has not worked so far as a shared universe. Whether it's creative difference, entangled storylines or under-developed characters, the DCEU has had many drawbacks and while that can't be ignored, it's also fair to acknowledge that most of their solo films have worked quite well. Looking at 'Man of Steel', 'Wonder Woman' and now 'Aquaman', they've all worked because they focused primarily on the characters in the movie rather than building a universe.
For some time it's been apparent that Warner Bros. have wanted to play catchup with Marvel and when that didn't work, they tried a more "Marvel" approach with 'Justice League' but essentially failed due to creative differences and the studio constantly interferring. Recently, Warner Bros. Chairman Toby Emmerich had stated that the DCEU will focus less on being a shared universe. This approach is probably the only valid way to go as of now for the DCEU without completely rebooting it. This approach allows for characters to be developed in ways that would allow the audience to care deeply for the characters and be invested in their journey/story rather than rushing the introduction of a new character just so that they could be featured in the next big crossover movie. The reason we all love Captain America, Iron Man, Thor and more in the MCU is because they've had time to develop and with that, they've grown to become characters we love.
Rushing into a big crossover movie like 'Justice League' was a bad idea primarily because half the movie focused on getting to know some characters for the first time - Cyborg, Flash and Aquaman. Prior to 'Justice League' we hadn't even gotten a Batman movie yet, all we've seen from him at the point was in 'Batman v Superman: Dawn of Justice' which simply wasn't enough for the audience to fully get to know that version of the character. Before a big crossover movie, we needed solo movies for the main characters involved in 'Justice League' so that as the audience, we actually know who they are but also, the movie would then have more time to spend on developing the villain and the overall story for the movie.
With solo movies also comes bigger stories for characters that aren't as well-known. The reason I enjoyed 'Aquaman' so much was simply because the movie told its story well and really fleshed out the characters involved. More importantly I had never read an 'Aquaman' comic book prior to watching the movie so going into the movie, I wasn't too educated on the characters and their lore/stories. This was my first proper insight on the character and I absolutely loved it because of its detail and because after the movie, I actually went on to read Geoff Johns run of Aquaman in the New 52. Solo movies for characters that aren't as well known are extremely vital not just to increase the popularity of that character but to give the audience a first experience and making it an enjoyable one.
Warner Bros. don't need to play catchup or worry about big crossover movies as of right now, instead they need to focus on developing their characters and giving them meaningful, interesting and fun stories. After watching 'Aquaman' I can honestly say I'm excited for 'Shazam' but I'm not putting all my trust in simply because as the audience, we deserve to watch these characters shine. What do you think though? Do you like this approach more or were you hoping for more big crossover movies?