Braves scored less than 700 runs in both 2013 and 2014. That happened only one other time (2011) during Wren's tenure. Now, granted, the decline in offense across baseball is a trend, but I don't think anyone could contend that replacing Chipper Jones with Chris Johnson and Brian McCann (even though he was in decline) with Evan Gattis didn't have a marked effect on the Braves' offense. You think of some of the other position flips (Escobar for Alex Gonzalez, Bourn for M. Upton) that have happened over the years and you can see how things have fallen off.
There are a lot of ways to score runs. Power has been the most reliable way to do that and will continue to be, but I don't see how anyone can deny that the team became more one-dimensional in 2013 and 2014 and the inability to put strikes in play is a gaping weakness. You can't put runners in motion if the guy at the plate can't put the bat on the ball. It was just a bad mix of players.