I tend to agree, STNG could have been more dangerous, and it didn't really have the censors that NBC did. There were quite a few topical episodes, though rarely to the point that they were controversial(slavery is bad, social underclasses are persecuted, etc). I do feel there would have been more that had that reaction if it weren't scifi and on syndication.
There were a few episodes that I recall people mentioned even at the time where they were surprised at the lack of media attention.
Gene Roddenberry pointed out "Who Watches the Watchers" as one of the ones he was most proud of. I also recalled wondering why there wasn't more protest over this episode.
"The Wounded" was also an episode that surprisingly didn't get a lot of reaction because it aired around the time of the 1st Gulf War...one of the most popular wars in American history, and the episode was an anti-Gulf War episode.
Arsenal of Freedom was a clear Oliver North commentary that masked itself as a cold war parable. Encounter at Farpoint also chose the Q US Marine dress uniform for this reason.
There were also episodes about terrorism in TNG which was a touchy subject back then and even more so now. Gene's viewpoint that made it into certain episodes was that there were 2 sides to the story, and more killing and weapons created more terrorists..just as we have seen with George W's nonsense in the 2000s that has created more terrorism and ISIS. One of these episodes was banned for a time in England.
Gene's direct view made it into "Symbiosis", even though the episode was not as effective it could have been. Far from being a "just say no" episode Gene felt abused substances were a crutch people used, and there was something much deeper into why people took them(including himself). Hence the storyline where Crusher discovers they don't actually need the "medicine" anymore..a twist that reveals parallels with the hidden reasons people use drugs. The episode itself is controversial with Trekkies, but not outside of ST.
These are just off the top of my head.
These were generally topics that were broader and not easily commented on in something like Maude or Archie Bunker. As a whole, STNG was probably the most liberal show (or at least drama) ever aired in the US. Even throwaway lines and such established this point of view even if the episodes weren't based on it.
RAMA
Which episode, exactly?
Shows like The Bold Ones, All in the Family, Maude, Lou Grant, and Hill Street Blues took more chances (politically and in terms of narrative innovation) than Star Trek: The Next Generation ever did, and they all did it on network television before TNG was even on the air.