I actually didn't have a huge problem with McNulty's arc or twist. It was outlandish but it feels organic not just from a character perspective, but from the rift between homicide detectives and the medical examiners office. In Simon's book, "Homicide", there's a chapter focusing on a death that the coroner declines to classify as a homicide. The detective, however, keeps pursuing the case, which is problematic because there are plenty of active homicide cases to spend time on. He eventually cracks the case but it's presented as the detective going above and beyond given the politics/concerns of the department.
So a "good guy" detective like McNulty fabricating evidence seems like an extreme twist, but not so much the idea that a good guy detective feels that some homicides aren't given enough attention. And McNulty, by this point in the show, feels like a character who is tired of all this shit but also has seen how he's gotten away with being a self-righteous dick who bucks the bureaucracy (from the very first episode). And the difference in opinion between the medical examiner and the police can be very problematic, since the former's designation is what ultimately makes a case a homicide or not.
IMO, the 5th season is the worst because of the newspaper setting. As a journalist, it wasn't particularly compelling to me. I mean, it may be the most realistic depiction of a newspaper on TV, and maybe familiarity breeds contempt, but the core problem is that it's not well-developed. The key flaw is that the "villains" of the newspaper setting, Scott Templeton (the reporter) and his enabling editors, are given no qualities beyond being caricatures of bad/evil journalists. This is the same reason why I feel Lieutenant Marimow (named after a Baltimore Sun whom Simon despised) is also a very weak character.
Compare the shallowness of the 5th season bad-guy journalists to the 3rd-season bad guy politicians, like Clay Davis. Davis is most definitely a corrupt character, but besides having an amazing catchphrase ("Shiiiiiiiiiiiiiiiiiiiiiiii-iiiit!"), he's still got some moral complexity behind him. I think this is best shown in the hilarious scene in the 5th season in which he takes the stand in his corruption trial with such dramatic finesse that he gets acquitted. Davis may be corrupt, but you can see why his community loves him. [0]
I'm not sure how you could make the 5th season journalists interesting, and I'm not sure Simon could either. His rants against the real-life Marimow and the Sun are lengthy and legendary [1], and this was after he was famous for The Wire. Simon is a die-hard defender of the sanctity of journalism and I think he let that overtake his sensibilities when writing the 5th season.
So a "good guy" detective like McNulty fabricating evidence seems like an extreme twist, but not so much the idea that a good guy detective feels that some homicides aren't given enough attention. And McNulty, by this point in the show, feels like a character who is tired of all this shit but also has seen how he's gotten away with being a self-righteous dick who bucks the bureaucracy (from the very first episode). And the difference in opinion between the medical examiner and the police can be very problematic, since the former's designation is what ultimately makes a case a homicide or not.
IMO, the 5th season is the worst because of the newspaper setting. As a journalist, it wasn't particularly compelling to me. I mean, it may be the most realistic depiction of a newspaper on TV, and maybe familiarity breeds contempt, but the core problem is that it's not well-developed. The key flaw is that the "villains" of the newspaper setting, Scott Templeton (the reporter) and his enabling editors, are given no qualities beyond being caricatures of bad/evil journalists. This is the same reason why I feel Lieutenant Marimow (named after a Baltimore Sun whom Simon despised) is also a very weak character.
Compare the shallowness of the 5th season bad-guy journalists to the 3rd-season bad guy politicians, like Clay Davis. Davis is most definitely a corrupt character, but besides having an amazing catchphrase ("Shiiiiiiiiiiiiiiiiiiiiiiii-iiiit!"), he's still got some moral complexity behind him. I think this is best shown in the hilarious scene in the 5th season in which he takes the stand in his corruption trial with such dramatic finesse that he gets acquitted. Davis may be corrupt, but you can see why his community loves him. [0]
I'm not sure how you could make the 5th season journalists interesting, and I'm not sure Simon could either. His rants against the real-life Marimow and the Sun are lengthy and legendary [1], and this was after he was famous for The Wire. Simon is a die-hard defender of the sanctity of journalism and I think he let that overtake his sensibilities when writing the 5th season.
[0] https://www.youtube.com/watch?v=bAQv6KTfQow
[1] http://jimromenesko.com/2012/04/05/david-simon-bill-marimow-...