With the news that Gal Gadot is definitely Wonder Woman in the sequel, all those rumors about Nightwing and Flash also being in it feels a lot more like a possibility. It's giving me the Iron Man 2 feeling with Marvel so quick to get to the Avengers, they just threw in a lot of SHIELD, easter eggs and references, and it was frankly kind of a mess. That's what Batman vs. Superman feels like. DC wants to jump the gun on Justice League and is throwing as many elements at it as possible to show off the larger DC universe.
I enjoyed Man of Steel, but it was missing a lot of character development and didn't really establish Superman's world, now we're throwing in a bunch of other characters. They could all still just be glorified cameos, but it would still be distracting to have these characters pop up, say a line and disappear.
Then there's the build up that I feel we're being cheated out of. I remember the excitement of seeing Marvel's big three on screen for the first time in Avengers after each having their own solo films, with SHIELD being the link. Here we have DC's big three sharing the screen for the first time in a Man of Steel sequel (with possibly others) with only Superman having a solo outing beforehand. It takes away from the eventual Justice League movie.