Has this ever happened to you? You watch two episodes of a TV series and, hoping it gets better, watch a 3rd episode. By the time you realize this is NOT going to be a favorite, you've invested so much time learning the characters and the story that you're tempted to keep watching. Like calling a poker bet with a bad hand because you've already invested so much in the pot you watch another episode instead of looking for something better.
This just happened to me with Mr. Mercedes. This crime drama has 7.7 imdb and 91% RT so it seemed a good bet. It's based on some Stephen King novels. I was never his fan but Shawshank Redemption is an OK movie (if somewhat over-rated).
I'll give Mr. Mercedes 5.5, far below the threshold needed to click the Start button. There's so much to dislike I hardly know where to start. Most of the characters are unsympathetic; the story fails. Long subplots are introduced that contribute very little. I'd assumed it was a 6- or 8-episode miniseries and was ready to quit it anyway; then discovered it's 30 episodes, with the same tedious characters and story spread over 3 seasons! Ugh.
I want to nitpick about its music. This is not an important reason to dislike the series but I think demonstrates the incompetence.
I know nothing about the craft of adding music to film. Sometimes it's just background or mood music for the viewer, but sometimes it's a song that character(s) in the film are listening to. But what about this absurdity? :-- The hero is at home, starts his phonograph and a song begins. The scene shifts to the villain's home on the other side of town while the song continues, without missing a beat. The song continues inside the villain's house, in his driveway, but stops abruptly when he closes his car door. This was so jarring and so stupid that I clicked OFF then and there.