Some of you need to Google more. Haha.
Lindsey wants to make new music. Fleetwood and J. McVie do not. Nicks is indifferent. She didn't partake in the "Buckingham/McVie" because she was in solo mode, and notoriously, she doesn't mix (like Phil and Genesis). He is notoriously NOT in "nostalgia mode" and wants to move forward with or without the Mac. As I understand it, that's the beef with this tour. I could well be wrong, because above all things, Buckingham is a really odd duck.
His interview with Dan Rather (it should be on YouTube) is really interesting. Sheds a lot of light on him and his way of thinking.