According to director Peter Segal, who was once in line to do a Shazam movie:
“Now that Superman is being invigorated and going up against Batman, I
think it’s difficult for DC to figure out how to launch this character
in the wake of Superman’s resurgence.”
I mean, you can't have two similar movies out there, that would totally not work. This is why you can't make shit happen DC, this is why Marvel keeps spanking you at the box office. You just don't try. Sure you FINALLY are going to do a Superman/Batman movie, but Marvel as at least tried to get damn near every major franchise out there. Yeah the results have been mixed at times, but still you have to look pretty hard to find major Marvel characters that haven't been on the big screen.
This is why when I heard that Wonder Woman would be in the new Superman/Batman movie and played by Gal Gadot I wasn't upset. Sure she's a horrendous cast choice, but I'm just happy to see DC is at least daring to put the amazon on the big screen. At this point I'm just happy with effort from Warner Bros when it comes to these movies. I mean if Marvel is willing do a freaking Guardians of the Galaxy movie then you got no excuse to for this kind of cowardice.
So make a damn Shazam movie already. No reason not to.