The main plot lines suffered because it was underdeveloped with entirely to much time on characters who really did do much to drive the plot. You can completely remove the Fen side plot and the story doesn't change. He almost shut down the tracker and just about died trying to blow up the canon but except for almost deserting and almost getting his friend killed he accomplished almost nothing. I really don't understand his role in the series. Is he comic relief? Side kick? Trusted companion? Why is he even there?
Poe was interesting but way to much screen time and not enough calendar time was used movinh him from hothead to careful leader. In general there was to much time spent on the good guys fighting themselves and the bad guys fighting themselves not nearly enough of them fighting each other.
The reason I scored it as high as I did is that despite all the faults it was mostly fun to watch. While I was watching I enjoyed it and that matters more than how it holds up to post dissection.