First off, Johnson is one of the biggest stars in Hollywood right now, and he’s clearly excited to play Black Adam.
Shazam is the black sheep of the DC Extended Universe.
Second, Shazam could be just the breath of fresh air that the DCEU needs right now, akin to what Deadpool did for the X-Men franchise (and superhero movies in general).
Right now Shazam is slated for release in April 2019, but we suggest that Warner Bros and DC try to move that up as soon as possible.