I never felt there was any singular plot driving the world or the books. There are so many stories happening, and we still have Starks left who are all performing their role in this whole world-altering struggle going on right now.
The Starks are obviously the 'hero' types, and we want to root for their family as they struggle to get by and as horrible things happen to them. But the rest of the people in the world are just as important. It's sort of the whole point of the series really - life happens, things don't always work out the way you hope. What goes around doesn't always come back around. They made a lot of stupid mistakes (Ned and Robb) based on values they put ahead of others. Were they wrong? No, but look how far it got them.
We get to see the contrast of that in people like the Freys, Boltons, and Lannisters. Money and power is worth more than just living and loving to these people. Even their own families are practically expendable at the drop of a hat.