Crazy, I can't tell you how many people have called me methodical in my life about various different things. I'm 100% a planner, live a structured life, and not very spontaneous. I am a J to the extreme, just as my test showed: J - 100.
The problem with diplomacy is I have absolutely no foresight whatsoever. I have no idea what will happen even one turn out. I'm an INTJ, a Mastermind. I read that Mastermind's put efficiency ahead of everything else. So, for me, I REALLY want to plan out moves for years at a time, and when I started playing diplomacy I did just that, but I soon realized how inefficient I was being because things would always get all messed up by unanticipated moves, so then I'd get right back to planning out another couple years very precisely, then unexpected things would happen and I'd be back at the drawing board. Eventually I learned to not waste me time and not look too far ahead.
Also, here's another bit about Masterminds: "But before [Mastermind's] decide anything, they must do the research. Masterminds are highly theoretical, but they insist on looking at all available data before they embrace an idea." So, again, since I can't anticipate, I must wait for orders to get processed to have "all available data" to analyze for the next set of moves.
So, Crazy, does that make more sense? I'm good at coming up with a general game plan and working with others in a game of diplomacy to get to the ultimate goal, but exactly how my ally/allies and I get there is often much different than anything I could have thought up ahead of time, which I assume is really how it works for everyone.