It's not like the other Marvel or DC superhero films. Adjust your expectations to a kid's movie that's intelligent enough not to torture adults. And it might be a pretty good example, of like an 80s or 90s kids movie that's actually scary in parts, and shows more-realistic-than-typical-for-movies kids horsing around when they get access to super-powers.

The kids are orphans in a group foster home ( "group" foster home that has fewer actual children [6] than the home in which I was raised with my biological siblings [7]. The female head of the household has a bumper sticker than says "I'm a foster mom, what's your superpower?" in response to which my mother would be all "Hold my beer", on account of not only raising more kids, but giving birth to them too, plus taking in 2 teenage foster kids, and hosting nieces who needed a place to crash for months at a time when their parents' housing situation got messed up, and sometimes working part-time jobs and sewing vestments in the church attic at night) </soapbox>, which explains a lot about their conflict-driving behavior.

Billy Batson is a 14 year old habitual runaway in the foster system, who keeps trying to track down his birth mother, from whom he was separated at a carnival or fair as a toddler, and the resolution of that storyline might actually be a little heavy for some of the younger audience members. His roommate and self-appointed best friend and later sidekick, is Freddie Freeman, who is movie-disabled (he walks with one of those canes that wraps around the wrist), and a superhero aficionado, who also happens to live in a world where Superman and Batman are real, and he has the newspaper clippings, and souvenir batarang to prove it. Unlike losers and assholes such as fat Ned in Spider-man: Homecoming or Cisco Ramon or that little weenie in Supergirl, his behavior is explained by what we know about him. He's a disabled orphan, so his endangering the hero's secret identity and fixation on his powered friend make sense. Fat Ned is rich, for children's values. At the least, before he is old enough to have a job, he somehow obtained a Lego Death Star. So his stuff comes across as a spoiled twit who acts on impulse. And while there is a cute teenaged girl, Mary is another foster sibling and not remotely a love interest. When you get right down to it, the love interest in this movie is the foster family itself.

Mark Strong is an evil research person who was passed over for getting the Shazam power as a kid and so has been hunting down other sch aspirants for details he can use to go after the powers anyway, which he obtains by absorbing 7 demons representing the capital sins, who are the archenemies of the wizard who gives Billy the powers. There is some talk about Billy being a pure soul, but that doesn't quite track with his behavior, and I think a smarter move would have been to make him a choice of desperation due to Strong's attack. Anyway, once Billy has superpowers and begins behaving with all the subtlety and discretion one expects of a 14 year old who suddenly gets superstrength, an adlt appearance and immunity to bullets or falling from great heights, Strong tracks him down to steal his powers.

It appears that one real life US city besides Washington DC exists in the DCU: Philadelphia, which looks a lot more real than the fake cities in which the other films and shows are set, like Central City, Starling City, Coast City and National City. Plus, of course, Gotham and Metropolis. The former of which is often referred to as Gotham City (edit: I just remembered their police is the GCPD, so Gotham City is probably the official name), and the latter's name actually MEANS city... and Philadelphia supposedly means "city of brotherly love" so I guess that's why it's the only one to make it.

An interesting twist on the villain is an evil version of the hero bit is that the villain is an adult, and so way more competent than Billy and keeps kicking his ass, until the climatic confrontation in which Billy pulls off a tactic that I don't remember seeing in any of the trailers and might not be surprising to fans of the original medium, but I think goes further than they might expect.

The whole scope of the powers of Shazam aren't too clear. Shazam seems to be an acronym of legendary figures who are the inspiration for the powers, the wisdom of Solomon (which is distinctly lacking in the film), the strength of Hercules and the something, something of other people I can't remember, although I think the speed of Mercury accounts for the M. And Zeus is the Z, which makes sense along with a real Jewish person and two Roman named deities. Or not. But he's got speed, strength and is bulletproof, and to his surprise can fly, which means that's a secret bonus power or else he wasn't paying attention any better than I was when the wizard (Djimon Hounsou, playing a second DCEU character along with his MCU character, which has to be a first) enumerated them.

And for that matter, while a bad guy who possesses the embodiments of the capital sins might be comic book canon, their natures or relationship to said sins is not a thing, which is probably good, considering that he spends a lot of time attacking children with them, so we don't have to see what Lust is up to.

Besides Strong and Hounsou, Zachary Levi is well cast as the adult superhero version of Billy, and Jerry from The Walking Dead (the big Hispanic or Asian guy who wears football pads for armor) is the foster dad, and Lionel Luthor from Smallville is the villain's father, I am fairly certain. And there is a brief appearance from what might or might not be Henry Cavill's torso & limbs.

Long story short, even though it's definitively set in the same universe as the other DC movies, it's a very different sort of superhero movie, more like one of those things where a kid finds a magic thing or something from another planet and has fun with it and then gets imperiled and has to learn a lesson. Except because its a superhero franchise, he doesn't have to give up the cool thing at the end. And as I noted about "Man of Steel" the best way to make a superhero movie, for DC at least, might actually be to make another kind of movie, where the McGuffin is superpowers.

OTOH, I seem to be 180 degrees out of sync with the general public on the subject of the DCCU, post-Nolan/Batman, as I loved every movie with Henry Cavill and Jason Momoa. So your mileage may vary on this one. It's not great, but it's okay as long as you adjust your expectations, and as noted above, does some interesting things with the characters, especially for a kids movie.