It’s mostly a police procedural about crimes slightly too weird even for CSI Miami. And partially a somewhat OTT gangster saga. And a bit of a “hey look, a thing from Batman!” show.
Sometimes the former works reasonably well. The child-snatchers in episode two were pretty creepy. And then sometimes it does Balloonman. Not sure it was a good call to have the first major vigilante to emerge after the Wayne murders, in the third episode of the show, be so... hilarious.
The overall effect is a bit like a splicing of Batman Begins with Batman Returns, where the grim down-to-earth stuff is suddenly interrupted by ninjas and circuses. It reasonably reflects what Gotham is like in the comics, but the shifts seem less jarring there.
The design work to make it look like 70s-80s hellhole New York never cleaned up is great (and could provide fodder for loads of World Of Darkness visuals).
And it’s making its own continuity, separate from (a) the other DC shows and (b) the DC movies. So the built-in possibilities for crossovers have been deliberately cut. (And apparently Arrow and The Flash will be separate to the movies as well, with a movie version of The Flash announced several years in advance complete with casting a week after the first episode came on TV, which is... not the direction I would have gone.)
Ultimately, Gotham is a backdrop for Batman. Does the city need him or not?