…I’m not sure how much sense that makes either: let’s fly out on barely functional crafts with limited maneuverability to a bunch of AT-ATs and a big gun and hope it doesn’t fire until we are really close so we can shoot at it.
To quote Antiope in Wonder Woman “You expect the battle to be fair! A battle will never be fair!”
The rebels were using the ships they had left. It was either that or sit in the entrance to the cave, put a marshmallow on a stick, and yell incoming!
If they could have gone out on a Star Destroyer and blown a FO-sized hole in the ground, I suspect they would have.
Previously, Dominic assured us that the FO would have found a way in if Finn had destroyed the gun. Holding to that idea, it doesn’t make very much sense to expend lives and time delaying the FO’s entry instead of finding a way out. I know they were hoping allies would show up - really fast and with lots of firepower - so the question is how much longer would it take to destroy the door without the cannon.
This isn’t the kind of issue really important to me, but on reflection this was a bit like grabbing a butterknife to confront an armed burglar trying to break your door. Granted you might prefer to use a bazooka, but that’s neither here nor there.