I fear Superman Legacy and all other Gunn verse projects will be dead on arrival just like the Flash. No matter how good or bad the movies, the Snyder loyalists will boycott everything. They make up far more than the noisy minority some dismiss them as.
Nothing short of Snyder being put in charge of everything will ever appease them. Even Cavill wasn't immune to suspicion and hostility when it was suggested anyone other than Zack direct MoS 2.
It used to be Marvel vs DC. These days DC is fighting and killing itself.
I am a massive Zack Snyder fan. I think his DC stuff is the most unique, deep and interesting content that has spawned from comic books being adapted into movies and I love it to absolute bits. I also love other DC content, so I'm not 'only a Snyder fan', I just loved the story he was telling.
Even I disagree with this opinion about the DCU being DOA.
Sure, I think there are a larger amount of people that loved his stuff than people think or try to make people believe, but as soon as a reboot happens (the key is, it needs to be a FULL reboot), then most of the audience will move on. Maybe I won't, maybe I'm cool with the DC movies that I like and don't need any more unless they're Justice League 2 and 3 directed by Snyder. But that's just me. I'm not the person you have to get on board, you have to get the everyman to want to see these movies.
Any impact of Snyder is more overt when you look at a Flash movie going back in time to the first Snyder film! I never understood that decision- the people who love Man of Steel (the nostalgia you're preying on) don't want to watch a Flash movie that specifically exists to erase the version they loved from existence in the timeline. Bringing it back to this Batfleck suit- it's dreadful, and it makes you think about the BvS suit instead, and how cool that was. Snyder's absence is all over this movie due to its setting.
It won't be over the DCU stuff.
When Gunn's actual stuff starts, even if there's 'pushback' from massive Snyder fans like me, I think DC will be fine. The Flash bombing does not mean DC is dead, The Batman just made 770 million, Joker a billion. Those weren't Snyder movies and they did MORE than fine with the general populous. They weren't even Nolan movies.
In my opinion, their first priority has to be lowering budgets at the start of this universe. Makes their break-even points more manageable, and then you can work your way up to the huge blockbusters when you have garnered the support that makes that seem reasonable.