Thats exactly what it was about i think, shit carries on, and there will always be fresh mofos coming through to take on these roles.
Actually I think the metaphor for the serious isn't the shit stays the same. Theres a moment in the end montage where that punk kid from namod's get put in bracelets despite being knee high to the cop. Or that any decent reporter in the BS is off the big desk, and the one willing to lie gets the Pulitzer.
The point of the Wire is, the kids get younger, the game gets tougher earlier, and it spits out and ruins people younger and younger. Meanwhile the politicians play the same games, the cops duke the stats, and most real police walk away.
Who are the decent cops at the start of the series? Lester, Mc Nulty, Kema, Bunk, Daniels and Leander. At the end you have Carver, Kema, Bunk and Leander.
At the start of the series you have gangsters who attempt to live at some semblance of a code. Remember the complete outrage when Avon's boy's attacked Omar and his mum, on a Sunday, and shot her "church crown!".
Would Marlo live to a code.
Again I think the Wire is (and I ain't going to claim to be an expert) is attempt by the writers to distil 20 years of crime reporting in Baltimore into five series. Avon and Prop Joe represent the 70s and 80s gangsters trying to live by a code, Marlo is in essence crack. This ruthless new generation with no code, and is nothing but addiction, power and ruthlessness. The kids represent the generation in between. For example would Chris or Snoop bother to education their corner hoppers like D'angelo did, use chess as a metaphor?
Sorry I'm rambling now. But I really don't think it was a hey "it's all the same" that was the message of the wire, it was more, it was bad, it got worse, and we're now completely fucked. Unless we radically think American drug and social policy, it's going to be something we cannot recover from.