Very, very thin plot. The movie is simply wave of jokes and gags one after another. Half way through and nothing is happening. Hate BvS, Justice League and Suicide Squad? Although those films had it flaws, they were watchable at least until they were finished.
On contrary, I would have walk out of the cinema with Shazam. The only reason I am able to finish it is because I'm watching it on steaming at home. No wonder it made little money internationally. 366m against 250m budget is a failure. But american critics seem to love this. Speaking about tastes, isn't it?
In summary: worst than Whedon's Justice League. Very cringe-worthy.