I haven't finished the game yet, but I get it seems that they just didn't do the story justice. Been playing mult player a lot because single player is mostly a downer.
Some big choices made in previous games have very little consequence in this game, and that is not what I was expecting. I understand what some are saying about artistic expression, but if they took the easy path and didn't maintain the quality and promise of the previous versions, then they did a bad job.
A more complete ending is just a partial fix, and it should be completely free.