With the amount of talent we have and money I considered this season an epic and utter failure. To answer the question though, no if you fall short of winning it all doesn't mean it's a fail season. Look at the Astros. 2 World Series in 3 years and they fell just short this season however that isn't a fail. Still had an incredible season and came up short to a very good Nationals team.
If the Sox lost to the Astros last year I also wouldn't have considered that a fail. Actually there were many of us on here that thought the Astros could beat us. Had we won a World Series last year and then won the division this year but lost to the Astros I still consider that a fantastic year actually. But missing the playoffs the way we did with essentially the same talent from the year before that went down as one of the best teams in the history of the sport is an utter failure.
I think it's insane that some think we need to fire a manager the second we don't win a World Series. Yes there is big expectations in Boston, and we are not the Jays so we don't expect mediocre play HOWEVER that doesn't mean you fire a manger the first year we don't make the World Series. Some want Cora gone..... So to sum up, this year was an epic fail but if we won the division and lost in the playoffs I don't consider it a fail of a season. Baseball is the toughest sport to repeat for a reason. If someone is expecting us to win the World Series every year they need to get give their head a shake.