His parents felt like 2 people I would actually stumble across in Kansas, so I think that casting was pretty good. And yeah it would have been nice to have more characters fleshed out (like Hawkgirl), but this is also only the first chapter in an entire universe. I’m sure the side characters will become more fleshed out as we go. I thought it benefited the movie to have these extra characters, because this is supposed to be a universe where superheroes have been around for hundreds of years
It makes sense that Superman isn’t the only superhero in Metropolis, especially when that’s the main hub for superheroes in the comics. This movie is essentially the DC comics but on the big screen. This movie is the equivalent of opening a random Superman comic issue and jumping right in, which is why we dive right into the action with a world with lots of pre-established locations and characters