Three things come to mind about this scene.
1) Troi actively had to aim the saucer section toward the planet if the force of the drive section's explosion is what pushes them into the atmosphere. Space is big and she could have gone any other direction.
2) The windows break. These things are stated to be made of transparent aluminium and are supposed to stand up against the rigors of space travel and combat. But they break when the ship crashes? Lack of thinking things through.
3) The evacuation. Do they go through that dramatic sequence every time they seperate? I thought they whole point of the saucer seperation was to keep the families out of harm's way. Why the hell are the families even IN the drive section?
These are all just writing faults more than anything else. That was really the problem with Generations as a whole. Poor writing. The effects, while not terribly inspiring, where alright.