At the time of its release the first Shazam film was solid and generally fit in the "good" section of the DCEU.
However by the time Shazam 2 came out it was bad and generally fit in the "bad" section of the DCEU.
I don't think Shazam 2 was poorly directed, but the story didn't work at all and was ultimately a mess. So with that, it's difficult to blame anyone other than the director.
I'm glad Sandberg is taking another swing at something big because they seem like a nice person and I think they can do a good job.