DS9 made observations about humanity that contradict Roddenberrian wisdom and that weren't taken seriously until 2001. It was an 00s show that aired in the 90s.
Why did I hate the show when it aired? Because it contradicted Roddenberrian wisdom, of course.
Humans didn't progress over time. Take away their creature comforts and they're a bunch of savage beasts, even worse than the farengi. HERESY, teenager me said!
I think it's the opposite, people wanted to love the show. The highest rated Star Trek episode in history? The Emissary. But the fact is the number of people who want dark serial shows is far smaller than the number of people who want optimistic light heartedness. DS9 is what we want, but it's not what most of the Neilsen audience wants, unfortunately.