Age, injury and linear thinking caught up with the Giants. What I mean by linear is that they tried to follow the success of past years -- keep the core intact and replace as needed. But losing the effectiveness of four core relievers (Romo, Castilla, Afffeldt, and Lopez) plus two from the starting outfield (Pagan, Blanco) was too much. With fat paychecks due to Cueto, Posey, Cain and newcomer Melancon, plus an underacheiving farm system, there wasn't much to trade for or to trade with. Maybe things would be different had Bumgarner and left-hand reliever Will Smith not been injured. Pence and Crawford too.
There's no place to go but up. Bochy and company are getting a good look at a lot of kids and 2018 is an even-numbered year too. We can't win all of them.