This is another episode that could've been so much better than it ultimately was, and unfortunately has a lot of other Star Trek that's better, namely any Bajoran episode, whether in Next Generation itself or Deep Space Nine. It's also essentially a Dr. Crusher episode, and that's almost never a good thing.
"The High Ground" is about terrorism. Crusher is kidnapped by terrorists, in fact, and is forced to come to terms with their thoughts on why they're killing people to get their message across. Star Trek has had a shocking emphasis on terrorism over the years, which only changed in the aftermath of 9/11, when an entire storyline was built around it. We were meant to sympathize with the Bajorans who regularly participated in terrorist attacks, for example. The line was only drawn with the Maquis, who were summarily declared to be Federation rebels, enemies of Picard and Sisko and only reluctantly absorbed into Janeway's crew, on the strength of its more idealistic and qualified representatives.
Like other episodes that don't quite succeed, "High Ground" fails by featuring another alien-culture-of-the-week, which is something some Star Trek fans enjoy and also drives other fans crazy. Randomness is only effective when the central characters really connect, and as I said, this is a Crusher episode. Not the best way to connect.
Gates McFadden has the distinction of being the only franchise series regular to have a gap in their record. For many reasons, she was dropped from the Next Generation cast after the first season, only to return in the third and thereafter remain, including appearances in its four movies. Yet Beverly Crusher remained a maddeningly ineffective character, thanks to McFadden's remoteness as a performer. This is not to say that she wasn't memorable at moments, or that if you see her or one of her episodes you should immediately find the skip button. It's just that, she was a constant challenge. "The High Ground" is one such moment where the challenge turned out to be a failure.
It's also an episode that slips your mind the longer it's been since you've seen it. Sometimes a fresh viewing will fix this. "The Seventh" from Enterprise is an example of an episode that quickly redeems itself upon watching it again. I somehow doubt that "High Ground" is in that company. There are just too many episodes that handle the same material, for whatever reason.
You might think it gets better once Picard joins Crusher as a hostage, and yet the series so frequently dodged the obvious issue of their past (and sometimes future) relationship that it's no surprise that "High Ground" ignores it (or perhaps explains why it never happened, which may be a reason to give it another shot after all). A lot of the episode ends up defaulting to the typical series mode of negotiating and, well, taking the high ground, removing the crucial element Crusher herself can't provide.
franchise * series * essential * character
Memory Alpha summary.