I agree with this sober critique of the pacing of the more whodunit aspects of the show. I think the show did well in landing its thesis — that the criminal justice and penal systems are extremely messy and the people who make their livings or find themselves imprisoned by them very rarely proceed through them in a straight line or without making lots of devestating mistakes along the way.
I think the central issue with it “not being able to outrun the genre” is the audience’s thirst for a definitive ending to the story. Call it the “Serial” (i.e. the NPR podcast) paradox if anything. We don’t want to spend 8 hours diving deep into a review of the justice system if it doesn’t have a tidy finish.