Josh Hutcherson sums it up perfectly with:
As far as the story goes you kind of see District 13 really start to formulate their plan to hit the Capitol, and it becomes really about physically making the war and making the change to try to fight for the people. Fight for the freedom.
Jennifer Lawrence talks about both Mockingjay Part 1 and Mockingjay Part 2, saying:
There are no games in this movie. There’s no fantastical part of it. We’re really moving into the war that’s brewing between District 13 and the Capitol. So we start to see a lot more of the Districts, and a lot more of the people starting to fight back.
Elizabeth Banks (who plays Effie Trinket) briefly summed up the Mockingjay Part 2 movie with:
The war rages on in part 2, and the rebels make it to the Capitol, eventually, and have to storm the palace and find Snow and get rid of him.
My favorite quote of this interview was from Donald Sutherland (who plays Snow) when he says in a very Snow-like, cryptic way:
I think they know that it’s a progression; we’ve gone from games to war.