I've posted this a few times, but since we got a DS9 specific thread ill discuss it again. The fact that previous Trek shows were the galaxy through the Federation's eyes and that DS9 was actually the Federation through the galaxy's eyes. This reexamination was very interesting to me. It finally made the Trek world feel less curated and more real. A lot of folks disliked the show because it broke Trek-isms like one ship and crew, and Rodenberry's utopia optimism, but I think it wasn't either of those things. The real culprit was exceptionalism, particularly for an American audience.
In the original series, you had a diverse cast under a BAMF captain. They went around solving problems by the seat of their pants. As long as they followed diligently captain BAMF as he always knew what to do. Essentially, a hammer punch and/or lip lock resolved anything the universe could throw at them. TNG was a bit more nuanced. We now had a diverse ship of the absolute best minds of the Federation. They tended to solve problems more with their mind, but still you had this exceptional crew taming a violent and unreasonably wild yet endless supply of caricature aliens filled galaxy.
Then, you have DS9. The Federation is sent into a backwater system to play neutral party to a formerly occupied species and their captors. Neither of which wants them there. The station systems are not reliable, the species not satiated or defeated easily overnight, but problems that adapt and change over the entire series run. A lot of this had to do with the rise of serial television over episodic, but at the same time Trek was breaking a mold and moving into telling more nuanced story telling. The moraly grey aspects often appeared to chafe the utopia Gene set up, but I think it goes well beyond that in expectation of an exceptional crew blowing through a straw galaxy. YMMV.