And in doing so, it became "just a show". Entertaining, but nothing more. Certainly not inspirational, unlike the prior series.
It all depends on what you find inspirational, I guess.
I find the characters' journeys on DS9 to be the most inspirational writing in Trek. I like TNG and TOS a lot, but the way DS9 took what had been done on those shows and challenged it, struggled with it, rejected some of it... It's a lot healthier, really, as a way of looking at the world than some of what TNG had to say.
I do love TNG, and there are some inspiring episodes, no doubt. But on the whole, DS9 is the story I tend to go back to (speaking of the overall fabric of the show).
TOS is more of an acquired taste to me, as it was already decades-old before I watched any of it.