They cornered themselves by trying to make that future story span multiple games. Especially because everything was written around one character, Desmond Miles and later Layla Hasan. They could have done a “Who do you think you are?” type of format and introduce a new character every game who has to explore his past to solve a problem in their future and just make every story stand alone with an ending but in the same universe. That way they can write better stories without the bagage of the previous games. The whole save the world with the Pieces of Eden story was so dumb