First off the music doesn't fit. There are shows and movies that are period pieces that mix in modern music well, but this is absolutely not one of those. They just randomly start blasting music that doesn't fit the tone of the scene, which throws the mood off and just feels confused.
Secondly, the writing goes from period appropriate to modern English with modem slang, then back again, which is unbearably noticeable.
Thirdly, the main characters are street kids and are somehow really well educated and they're unrealistically well- spoken, and proper, which obviously makes no sense.
The acting is actually pretty good, and so is the story itself, but my first two points makes the show almost unwatchable. The bottomline is they were trying way to hard to be so many things