DS9 great example of non utopia.
It's a great example of the struggles to achieve utopia and the decisions made in pursuit of those goals.
Shit TNG had a ton of examples of how Starfleet isn’t perfect and there’s still political bs.
Practically a running joke that every Starfleet Admiral is trash, sure.
But they're typically described as contrary to the ideological underpinnings of Star Fleet, not agents within a system that rewards and reproduces corruption.