This is a huge understatement.
The story and pacing was a complete mess of epic proportions and lets not even talk about chapter 13
Game is the definition of development hell, the amount of cut content and with how many times the story was redone has to be some kind of record in the industry. It was the most mishmash hogwash thrown together game in the series.
As much as 13 sucked at least it felt like one complete game. They tried for two years to fix 15 and its still a mess. All the DLC and Kingsglaive should have just been part of the main game from the beginning