The whole reason that the DCEU has finally gotten good is because they’ve just let their directors basically do whatever they want. Shazam! Is probably the most connected to the outer universe and even then it’s used as a joke more than not. The fact that Zack Snyder’s Justice League is actually reviewing well and doing well and yet they’ve obviously not signed anymore with him is kinda a pinpoint of how they want the DCEU to be presented going forward. If a crossover isn’t done well I personally don’t think it should be done at all. We’ll have to wait and see how Flashpoint does but if Joker and The Batman or even WW84 are any indication it’s that continuity is not something they’re particularly interested in pursuing, even movies like Birds of Prey and The Suicide Squad are apparently so loosely connected by only one or two characters that it’s not really notable, which is in stark contrast to Marvel where everything is connected.
Personally, I think that’s a good thing. The directors and writers need creative freedom and one of the big reasons Marvel works so well is because they know HOW to offer that. Apparently they often outline the few things that need to happen in the movie and then let the director and writers do the rest. Thor Ragnarok for example basically said they need to be on Sakar, Asgard needs to be destroyed, Loki, Hulk, and Thor need to end up in space and then apparently Taika Waititi pretty much winged it for the rest of the movie. 85%, or some ludicrous number, of Thor Ragnarok was apparently unscripted.
DC rushed to start their Cinematic Universe and personally, at this point, they should just start over. And looking at the outline of Flashpoint, that looks like exactly what they intend on doing.