Getting Gilbert and allowing Emelin to play his strong side instead of Gorges hasn't made this team weaker. Gilbert has played well in the last month or so and gives us a much better transition game.
It has made us weaker, and not noticeably improved the transition game, although of course that was "the plan". Or hope. It hasn't worked out that way, a little too much emphasis was placed on which side the players played, although again understandable to "hope" that Emelin would have been better, though he hasn't been much, and it failed to consider how well Gorges plays on the right.
And for sure, there is not a "much better transition game" in effect with the team right now. You are quoting from the "the plan" which likely played into the trade, and it was all something which we all used to derive our hopes and felicitations from at the time of the move, for sure, but in hindsight, I don't see how anybody can think things have gone quite according to that plan. It failed, but again, through no fault of Gilbert's.
Or at least, it has failed for 30 games thus far. Things might come back around, particularly if Emelin does start playing noticeably better and/or if Gorges really does dissolve into some pale shadow of his former self. There is still time for that stuff to happen. Good thing is, it's a team game, and the composition of your #4/5/6 defenders isn't necessarily going to make or break your season anyway, as long as you have generally capable bodies in place, and Bergevin has done a good job getting generally capable bodies in place... Gilbert as the immediate fallback plan signing was part of that.