For me, the move to pinch-hit Wisdom for PCA was defensable when looked at as a single move at that point in time. I do believe Wisdom gave the Cubs a better chance to score a run (or runs) in that situation.
The problem was PCA being in the game to begin with. Yes, he is a defensive upgrade over Tauchman, but the Cubs were facing a Braves offense that was almost certain to mount some form of comeback. Even when the Cubs were up 6-0, it was too early in the game to be giving up offensive production when it was still entirely possibly that they might (and did) end up needing a few more runs to win the game.
Had Tauchman stayed in the game, the Cubs could have pinch hit Wisdom for him instead, then brought PCA in for defense in the 8th inning when it really mattered. Would things have been different with him in CF? Probably. But we'll never know for sure.