This is like complaining the Cs give up more 3s than they used t or that the Pats can't stop the pass anymore, and the Bruins don't fight as much.The Red Sox are league average in allowing home runs. The MLB ave is 72; the Sox have allowed 71. NL teams have allowed an league average of 69, which you'd expect actually to be lower because of facing basically eight-hitter lineups.
The Red Sox have not had a problem "keeping the ball in the park." Every team has.