How so? How are humans in DS9 "less evolved" than those in TNG? The humans in TNG were flawed; Geordi was reserved, Picard was arrogant, Riker famously had stink-nuts, and admiral after admiral was shown to be corrupt. As far as I'm concerned, the notion that humanity is evolved is little more than propaganda that Federation diplomats, including Picard, are forced to spread around the galaxy, there's almost no evidence for it in the show itself.
The characters on TNG were flawed, perhaps not flawed enough, but once Michael Piller took over there is enough there to balance out the sci-fi adventure and give the show a second dimension.
There's a lot of crap in the early seasons I just feel I have to ignore. At some point Doctor Crusher expresses astonishment and a certain patronizing contempt that humans in the past actually feared death
, the implication being that the characters on TNG don't anymore.
I'm not sure what that even means or how one would build a sci-fi adventure show on the principal that these characters have no fear of death and are therefore indifferent to the dangers they are facing.
There's much less of this obnoxious type of declaration in the later seasons (thankfully), though it does resurface from time to time, such as in Time's Arrow