Sorry, but the Batman vs. Superman x 3 plotline wasn't that strong.
Of the two "superhero conflict" movies released in 2016,
Batman v. Superman: Dawn of Justice was the one with the
believable reason for heroes to clash, with its plot coherently justified by the events of
Man of Steel, introduced the best Batman/Bruce Wayne ever put on film (or second best after Bale, depending on your mileage), and a filmed Luthor who lived up to the megalomaniacal (and atheistic) behavior displayed in his greatest comic-book stories, all perfectly introducing / weaving in Wonder Woman. Audiences wanted more of this then-building DCEU.
Except it isn't really him making the call. James is a hired Gunn (pun firmly intended). What he is doing is simply carrying out the wishes of Zaslav. Zaslav is the one who has been crying out that Superman should be a billiion dollar movie (which i actually agree with,though certainly not how Zaslav is doing it), and Zaslav is the one demanding a 10 year plan.
Gunn is in charge of DCU's creative development, he was the one who had the now-infamous conversation with Cavill (who had agreed to return as Superman up to that point), and thanks to
his decision to end the MoS continuity and start with some younger-years Superman, Cavill was dismissed. The responsibility rests with Gunn.
Doing the math, that will mean Cavill will be in the role for 20 years at the end of it...while he might still look good at that age, he won't be able to carry Superman further than that.
Irrelevant concern in this era of de-aging actors. However, I'd think if actors' ages were a concern at all, the discussion would land on Holland still portraying teenaged Parker, when Holland does not look like anyone in the neighborhood of being teenaged, which was glaring in his most recent appearance as the character.
By the way, Gunn seems to be trying to be as diplomatic and respectful as possible, and i don't see any evidence countering that.
The decision was still dick-headed. In the world of film, if there's
one actor audiences wanted to see return to a role, it was not Downey jr. as Stark. Not Evans as Captain America, but Cavill as Superman. The run-up to and announcement that he was not only appearing in
Black Adam, but returning to the DCEU was one of the biggest,
positive news events for movies this year (if not for the past few years), with fan reactions ever-proving that they loved his interpretation in the stories written for him. Now, that's been ripped to shreds thanks to "DC's Kevin Feige" deciding to bury the technically still-active MoS continuity. There's no surprise that blame is aimed at Gunn.
). It just wasn't Superman. There were hints here and there for sure. And again I'll say that's not on him but the people writing and directing.