Exactly right. The show was at it's core, about a marriage. The purgatory of living the rest of your life after leaving your children is almost unbearably sad, particularly considering how their last conversations were with both. And both kids will hate them forever.
It was also a show about friendship and betrayal, as well as the sacrifices that one makes in the service of an ideal. Stan certainly had his, as well as his own moments from staying the course. But Philip and Liz sacrificed everything, including the only pure things they actually had (their kids) for their country. While they stood looking at the twinkling lights of Moscow, it seemed as if they could almost get to the point of thinking it was all for a just cause, but of course the viewer knows that the idea of Russia they had in their heads really no longer existed by the time they returned, and what waited for them wouldn't be be there for much longer. So, all that sacrifice, betrayal, loss and an eternal purgatory of abandoning their children for...what?
I could have envisioned a much more dramatic ending as many here, but for this show it fits. Perhaps it was a little anticlimactic in the end, but it made the price they paid even more severe.
As a parent, that final call to Henry was just gutting, as was the sight of Paige on the platform. These are the casualties of war.