You know, I had a thought about DS9 and Longinus' dislike for it.
Star Trek's utopic world was always something of a puzzle, really. How do you build and maintain such a world? Would you not need some measure of violence and deceit to do both? Would the empires around you not see your presence as an existential threat due to the reminder you represent to their own people that there is such a life possible for them? Would they then not seek to eliminate you by any means necessary? And in that scenario, would you not need to defend against these aggressions, and does this not entail being less than nice or principled about it?
TOS and TNG always had hints that the Federation was defended through more shady means, while the population of the inner planets lived their happy lives, turning a blind eye to that. DS9 was just more open about it, because it was told from the point of view of the very people who provided that security, comfort and obliviousness. Sisko was put in that position because he was the man for the job, and when things got really rough he did what was necessary to safeguard the lives and standards of living of Federation citizens in a way Picard and Kirk never had to because they were usually away from those existential threats.
DS9 is not that different from its predecessors; it just shows us the cost that has to be paid for paradise.