For the ending, the main writer in charge of the show left after season 4, so season 5 was written by a less experienced team. I noticed that, even in the first scene of the season, it's much more on the nose and lacked the subtly and nuance of the earlier seasons. Although I couldn't keep watching because I genuinely couldn't bear watch Mcnulty get worse again right after he got better.
Overall i like it. I think it helped me understand "lumpenproletariat" more as a concept. I think the writing was astoundingly great for an American cop show (or American shows in general).
And I feel like the politic plot pines were very important, to show
A.How lone wolves trying to change things can get kicked to the curb very easily
B.How decisions are actually made by Bourgeois political agents
C.How easily even..."noble" people get corrupted or get stuck trying to bring about reform even on local levels on local issues.
The second season is probably my favorite, but it is competing with the fourth season for that spot so its hard to choose. The longshoremen union workers had a very realistic and honestly just heartwrenching plot. It's been a while since I watched it though so I can't go in more detail.
My favorite character though is probably Stringer Bell. He's this really interesting Don Quixote archetype, just instead of idolizing chivalrous feudalism he idolized ruthless capitalism. He also has my favorite line of "Are you taking notes on a criminal fucking conspiracy?"