Is the low rating due to fan expectation or because the show is bad?
I watched the show and it was good. Not great but I expected that. They did a good job and it is for young adults. The lead characters did a good job. It was a plain investigative show based on book. No special effects, overly dramatic moments or high budget.
It stays in its lane and does not overreach nor underreach. It delivers exactly what you expect from the title. The element of realism and pragmatism is what sets it apart. You don't get Sherlock here, just a girl who solves crime like its homework.